Influenced by this consideration, and the similarity of the court in general outline, Walcott concluded that Astj^aspis was connected on the one hand with the "cephalaspidian fishes of the Silurian of Russia." this was described by the organization of Psamosteusis .^. The occurrence is interesting in its account of demonstrating the wide distribution of the genus in Upper Devonian time, and also because it is difficult to trace a path of domestication which would connect these events with its nearest part in the hemis- ]) here, B.
This species, known only from fragmentary pieces of skin armor and appendages, is abundant in the cat rock along the border line between New York and Pennsylvania. A specimen in the Lacoe collection requires special notice, because it was figured and described by Copeas as a pectoral limb of the genus Holonerna. In the course of his investigation of the Wildungen fish, characteristic certam remains of skin-shaving plates and tubercular ornaments were found, similar to those also in the Middle Wisconsin Sea, and reminiscent of the loss of the skin of the Myriacan- it.
DIPNOI
To date, however, it has remained the most complete fin spine of the species and genus uncovered to date. In the specimen here shown the entire outline of the inserted part of the base is clearly shown, and the similarity of the inserted part to the bases of chimeroid head spines, and also those of carbonaceous forms such as Physonemus.
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Giirich Mn1891, and some further changes in the recovery of Coccosteus were proposed in a series of articles by Otto Jaekel, published in the first decade of this century. Concerning one of the restorations put forward by the latter author, that of the cranial shield of his so-called Pachyostushvlla, it should be noted that the pattern of plate arrangement is not exactly the same as observed in primitive species of DinicUTiys. This will become clear from a comparison of the accompanying text figures 3 and 4, with the Wildungen species and D.lid.modeus from the New York Devonian, respectively. To date, no evidence has been found for the occurrence of a pair of vomerine teeth in this genus, corresponding to the thus produced 'premaxiUary' teeth (in reality vomerine) of Dinichtliys; but that some such elements had been developed was at least made plausible by analogy with Dinomylostoma, from the Portageshal in Western New York.
Said evidence is represented by a single large composite plate representing the fused links of the anterior pair of philosomic tooth plates, found in an isolated state and originally described by Louis Hussakof' in 1909 as a type of dis-. The present writer proposed that the new genus proposed by Dr. Husakof, and named DinognatJius, should be retained in a provisional sense.
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TELEOSTOML
CARBONIFEROUS SYSTEM
ELASMOBRANCHII
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Woodward in his Catalog of Fossil FishesintheBritish Museum (Part 1, p. 56), "no teeth of this genus having hitherto found a natural association, it is impossible to distinguish between specific characters and the variations exhibited. The teeth of this species attain large size, and according to the original authors It is possible to distinguish between the associated upper and lower tooth coats Two suction teeth, which we interpret as indicating a median unpaired row, have already been counted by Newberry under the erroneous designation P.glyptus; of the same species.
The unique specimen serving as a type for this species shows the two sets of crush plates belonging to both halves of the same jaw, and the original author postulates that these elements lie in their undisturbed natural position. Again, in his discussion of the teeth commonly known as Deltodus occidentalism, he takes it upon himself to transfer this species to Sandalodus, 'because there is apparently but one tooth in each ramus of the jaw'. This last statement is merely an assumption based on negative evidence, and no evidence has yet been provided to show that the number of dental elements in the mouth of Sandalodus was the same as in Deltodus. 261genus Sandalodus, solely due to our lack of knowledge of the genus Sandalodus, solely due to our lack of knowledge of the anterior components of the complete dentition.
ICHTHYODORULITES
In this, however, as in most examples of this species and of Physonemus from St.
LIST OF SPECIES OF CTENACANTHUS OCCURRING IN THE MISSIS- SIPPIAN SERIES
Spines of this species are extremely rare in the Lower Carboniferous of the Mississippi Valley, and few perfect examples have been obtained from this country or Great Britain. Of this genus two European and two American species have been described, all forms closely corresponding to the Physonemus type of the frontal spine, but differing from it in that the spines are divergent; that is, they consist of two branches extending opposite each other. The soft spine is somewhat asymmetrical and was probably located on either side of the head region, while the bilaterally symmetric PJiysonemus type of the frontal spine occupied an anoccipital position.
An abrupt turn in the direction of the spine occurs about the middle of its length, whereby the distal part of the axis deviates at right angles from the proximal part. The characteristic characters of the greatly elongated base in spines belonging to this species remained unsuspected in the publication of Newberry's posthumous paper in 1897, in which a single large and nearly complete spine was described and illustrated. A small fragment from the Chester limestone of Ilhnois, described by St. John and Worthen as Oracanthus rectus, shows a tendency of the tubercles of the exposed portion to fuse into irregular transverse series.
TELEOSTOMI
We should probably assign to this species half a dozen specimens in the collection of the United States National Museum, all of which are quite distorted and imperfect, but agree in size and detail of ornamentation of the cranial plates with C. Owing to the fact that Newberry recognized the occurrence of this species in Mazon Creek locality makes it more likely that we are indeed dealing with the already known form from Hamilton, Ohio, rather than an undescribed representative of the genus. In the latter respect the agreement with the specialized and problematic genus Tarrasius from the Lower Carboniferous of Scotland and also with Concliopoma gadiforme Kjier from the Lower Permian of Rhenish Prussia is to be noted.
It is an example formerly in the Lacoe collection, now the property of the United States National Museum, and cataloged as No. Thus, the exact definition of the end of the middle is indeterminate, the bones of the head are confused, and although the neuralland hemalarches are clearly shown that the anterior half of the trunk, they are visible. in the caudal region. This genus, apparently indicated by isolated patches on scales in the Upper Devonian rocks of this country, and represented by several species in the Lower Carboniferous of NewBrmiswick and the United States, continues into the Pemisylvanian in this country.
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FISHES OF THE TRIASSIC SYSTEM
For the purpose of the present contribution it is not considered practical to give an extended or detailed account of the large stock of fossil fishes from Mesozoic and Cenozoic horizons belonging to the collections of the United States National Museum, in view of the fact that the majority of them belong to known genera, whose anatomical structure is rather close to that of. From the Cordilleran region of this country a large quantity of fish remains, now in the National Museum Collection, was obtained by Dr.CD. Walcott in the years 1879-80, when he explored the Kanab Canyon of Utahand Arizona as his first work in connection with the United States Geological Survey. In the last decade, remains of the Shinarump Group of southwestern Colorado were discovered by Dr.
Whitman Cross, who showed that there are strong reasons for correlating the Triassic part of this group, as defined by Powell, with the lower part of the Dolores Formation in Colorado. Although the fish remains from this section are extremely fragmentary, the presence of the genera Lepidotus and Plwlidopliorus can be recognized with certainty; and on the first examination of this material, the writer concluded from their general point of view that they indicated an indication of Lias conditions.^ During the past year, however, more complete specimens of the genus Lepidotus were examined, the largest being the best preserved of which Chareillus-. The family was followed in the Triassic by other chondrosteans, which took the form of steel (Belonorhynchidae) and died out during this period.
Ten years later the second known species of Catopterus was described by Sir Phi Up Gray Egerton, when the new genus Dictyopyge was erected by him on the basis of reasonably well-preserved specimens from the Richmond coalfield in Virginia. Titer's observation to clarify the much-debated topic of the cranial osteology of this species and genus must first mention one of the original cotypes of C. To speak more particularly of cranial osteology, it must be admitted that hardly anything can be added to the facts already known.
This plate bears numerous fine, acutely conical teeth, and a small dentigerous premaxilla is also present, often found separated from the other mouth. The examples shown on the accompanying plates are the most perfect, and are in the collection made by Doctor Walcott on his first time. Although the collections were made more than 35 years ago by Doctor Walcott, in whose honor I have the pleasure to dedicate the species, it appears that no one else has obtained fish remains from the Utah Triassic, nor has any other species Lepidotus described.
The latter is important in view of the fact that the Triassic shale fauna has been found on LittleColorado, Arizona, in the San Juan Valley, Utah, not far from the Colorado River, at various points in southwestern Colorado, where Doctor Cross had been engaged in research for many years, and near Lander, Wyoming, where Dr.
FISHES OF THE JURASSIC SYSTEM
Das wunderschön erhaltene Exemplar auf Tafel 14, Abbildung 2, ist von Interesse, da es ein frühes Wachstumsstadium der Jungen dieser Art zeigt. Das Rostrum erscheint relativ länger als im Kopf und erstreckt sich über eine relativ größere Distanz vor dem Präsymphysenknochen. Dies beweist, dass bei dieser Art, wie auch bei Aspidorhynchus, die Schnauze und der Unterkiefer bereits in einem frühen Stadium ihre volle Entwicklung erreichen und danach nur noch an Dicke zunehmen. Auch hier besteht der Oberkiefer (mit Rost) aus den gleichen Elementen und ist insgesamt gleich gestaltet, nämlich der Abschnitt (^chan-crure), in den der Unterkiefer passt und den Agassiz ausdrücklich als exklusives Merkmal angibt von Asp. kommt auch in Bel. vor, allerdings etwas abgeflachter (was insbesondere bei B. milnsterid der Fall zu sein scheint).
BijAsp. Die relativ kurze Spitze des Unterkiefers dient als Vorkiefer. Bei Lichteinwirkung ist es oft schwierig, unechte Exemplare zu erkennen. Diese Gattung ist Propterics sehr ähnlich, wobei sich die Bub durch die Nichtverlängerung der vorderen Strahlen der Rückenflosse unterscheiden, die sehr weit voneinander entfernt sind. und im weniger tief gegabelten Charakter der Schwanzflosse.
Based on a very small (5 cm long), almost complete fish, the proportions of head and body being very similar to those (Cat. No. 8379, U.S.N.M.) of N.inimontis Thiol here, but with a more slender body shape , the two parts of the back are entirely separated, each consisting of about nine rays, and a posterior margin of scales smooth.
FISHES OF THE TERTIARY SYSTEM
There is also an abundant display of Eocene and Miocene ichthyic remains from the Atlantic coast region, and from the foreign Tertiary horizon several must be mentioned. In the following pages, some types of Cope not previously proposed are discussed, and two or three cAV species of tertiary fish are described. This family, which first appeared in the Eocene, is represented by several modern genera, two of which, Osteoglossum* and Arapaima, occur in South American rivers.
Museum (Cat. No. 4916), and has been carefully prepared to reveal the underside, free of the matrix. In this family, which includes forms of extremely small size, the mouth is extendable, teeth are present on the jaws and pharynx, but rarely on the palate; the palatoquadrate arch is more or less reduced; and the supraoccipital extends forward to the frontal, separating the parietal in the median line. As a small form that reaches a total length of about 5.5 cm, in which the length of the head and opercular apparatus is included three and a half times.
The holotype of this species (Cat. 4302a) and a large number of viU-preserved specimens from the Esmeralda Formation of western Nevada, recollected in the United States NationalMuseumcollec-. Fragmentary remains from the Lower Eocene have been assigned to Arius, and others from the Lower Miocene to Ameiurus. Based on a unique specimen without a locality label, but as far as can be judged from the appearance of the matrix, it appears to be derived from the Green River Eocene of Wyoming.
The holotype of this species is a nearly complete skeleton with a total length to the base of the caudal fin of 21.5 cm, with the length of the head including the supraocoipital process included three times. But in the almost complete skeleton we now consider, we find evidence that the typical expression of the genus Ameiurus, as we know it today, was already achieved in the early Tertiary, and has remained unchanged since then. Of the seven species described by Cope from Tertiary freshwater formations in this country, six are preserved in the National Museum of the United States.
In the second the primary spine is weak and thinner and there are 13 or 14 radii of the second dorsal fin; in this division belong P.
UNCERTAIN PLACE
EXPLANATION OF PLATES
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A complete skeleton on slab, Xf
