As indicated above, we believe that the conodonts are the teeth of primitive fish and not necessarily all of the same group. 8 PROCEEDINGS OF THE NATIONAL MUSEUM VOL.68 strongly developed main cusp usually with a variously modified undenticulated downward extension. Distinguished from its closest allies by the large size, straightness and strong anterior slope of the terminal points.
ART. 12 CLASSIFICATION OF CONODONTS ULRICH AND BASSLER H
The denticle next to the main tip is almost at right angles to the rod and the subsequent ones increase their slope very slowly to the end of the rod. Characterized by a greater curvature of both the main point with its downward extension and the teeth and the relatively equal length and strength of the lateral teeth of which there are seven. The front is essentially as in other species of the genus, except that there are no denticles on the bar, only two suckeis on the downward extension of the main cusp and the main cusp is more recurved than usual.
16 PEOCEEDINGS OF THE NATIONAL MUSEUM VOL. CS
ART. 12 CLASSIFICATION OF CONODONTS ULEICH AND BASSLER 17
Like Prioniodina except the denticles are odd, none particularly larger than the other. One end of the bar, presumed to be the posterior because of the slope of the denticles, is commonly produced into a blunt process. The anterior denticles are shorter and those in the middle half are of average size.
ART. 12 CLASSIFICATION OF CONODONTS ULRICH AND BASSLER 21 PRIONIODELLA CONFERTA, new species
Of the posterior teeth, the second and third from the main cusp are wider than the others, the last two are quite small. It is easily distinguished by the extreme difference between the size of the lateral series of denticles and the main cusp. AUT.12 CLASSIFICATION OF CONODONTS ULRICH AND BASSLER 23 genus but those on both sides of the main cusp are bilateral.
AUT. 12 CLASSIFICATION OF CONODONTS ULRICH AND BASSLER 23 genus but those on the two- sides of the main cusp are bilaterally
This neat species as based on Figures 12 and 13 is characterized by the rather strong even curvature of the rod, prominence although not large size of the main point, numerous, unequal, outwardly tapering denticles all sloping posteriorly and the small size of the protrusion at the bottom of the rod immediately below the main point. The strong curvature of the rod and the rather short and not large main point with an equal number of numerous denticles on each side will sufficiently distinguish this species which is, however. Bar rather strongly curved, main cusp slender, very long merging with the shorter denticle immediately in front, and this with all the others up to the anterior limb.
ART. 12 CLASSIFICATION OF CONODONTS ULRICH AND BASSLEE 25
It differs from all other species of the genus in the narrowness of the rod and the fine teeth which are closely arranged on one half and farther apart on the other. This species is intermediate in its characters between Prioniodina and Bryantodiis., the complete separation of the denticles being as in the former and the sharp lateral sides of the main point as in the latter. Characterized by the relatively very large size of the shai-p-edged main point and inconspicuous development of the denticles on llie.
The main characteristic of this species, in addition to its minimal size, is the great disparity in the size of the teeth and the main lip. The teeth on the TV ends of the bar are located further forward towards the outside of the bar. Posterior extension of the bar with eight somewhat unequal but rather strong teeth, the largest of Avhich may be about half the length of the main cusp.
The downward projection of the bar about rectangular to the axis of the bar and about half the length. It is distinguished by its considerable width, unusual flatness, sharp edges and a decided forward curvature of the main tip and more. The main characteristics of this genus are its outwardly bent corma, the greater length and spacing of the rounded needle-shaped teeth, and their usually unsymmetrical arrangement.
Also in that the teeth of the anterior half regularly decrease in length outwards while in L.
AKT. 12 CLASSIFICATION OF CONODONTS ULRICH AND BASSLER 33 bends backward so strongly that it is almost parallel with the direc-
Usually three denticles in front of the main point and one at its base, showing only on the inside, and two behind the head. The species is reminiscent of Hibhardena but the main point is not in the middle or directly over the swelling in the rod as in that genus. The relative straightness of the rod easily characterizes this species which in no other respects is much like L.
Similar in the angulation of the bar to Z. nrcuata and L. subangulata, but easily distinguished from both of them by the very rough, alternatinir size of the denticles on the posterior part. Tooth strongly bent outwards, but the distinct separation of the main cusp and its strongly denticulated downward-inward projection (an-. The very considerable strength of the denticles on both ends of the bar determined the vo- visional location under Lonchodhm.
Owing to the curved form the tooth is usually broken, but unless it is broken so that the two ends of the rod separate and lie nearer in a plane than natural, the teeth of the anteri (n-end are not visible in a view from the convex side) The main cusp is relatively shorter and somewhat sharp-edged and the disproportion between its length and the denticles on the posterior portion of rod is much less. The length of all but the first of these six posterior denticles is almost or quite the same as that of the main cusp itself.
A subcentrally placed denticle can be called the main cusp being relatively larger and longer than the others.
ABT. 12 CLASSIFICATION OF CONODONTS ULEICH AND BASSLER 37 LONCHODINA RECTANGULATA, new species
In this species the angulation of the bar is less, making a much wider angle between the arms, each of which is longer and bears nine relatively short denticles in all the specimens seen. The head tip is very long, slender, parallel-sided and appears particularly elongated due to the shortness of the lateral denticles. Although apparently bilaterally symmetrical, consisting of a larger central main cusp with smaller denticles on either side, i.
Stipe long and straight, with as many as ten small teeth in front of the strong long main point and a long series of numerous small slender teeth often varying in size behind it, those of each set about equal in size. This genus includes a number of species with relationships on the one hand to Lonchodina and perhaps more specifically to Prioniodina and on the other to Prioniodus, but with other characters that are clearly its own. Most of the species have an almost straight rod, but have a relatively strong and very long denticle near the wider end with a long series of smaller teeth, typically in varying sizes, behind it.
This general arrangement suggests that Prioniodus, from which HindeodeUa is distinguished, has an anterior dentate part with 1 to 8 or 10 small denticles developed in front of the main cusp and without the downwardly projecting process, although this is simulated by the downward deflection. of the corresponding part. The division of the tooth into two dentate parts suggests a relationship with Prioniodina and more particularly with Euprioniodina, from which it is distinguished by the slimmer, longer and straighter rod and other peculiarities that become apparent when comparing the images of their respective species . The species is particularly characterized by the smallness of the denticles and their marked alternation in size, usually three very small denticles occurring in the space between two and being much larger.
The main tooth is two or three times as long as those on the bar; in front of it a narrow toothless space and then occurs a grouj) of three or four teeth, of which the last is the largest.
ART. 12 CLASSIFICATION OF CONODONTS ULRICH AND BASSLER 41 HINDEODELLA SUBEQUALIS, new species
As our copies of the original illustrations show, it is possible that this genus is not a conodont. Even the middle ridge is not represented on the larger of the two, which moreover comes from very different geological horizons. The present species differs from all others, and must be regarded as a doubtful form of the genus.
Lower (8) and upper (10) views of the same specimen as Fig. 9, representing a three-quarter basal and end view. Again, the front of the plate has developed a pair of low ridges that diverge posteriorly. Species distinguished by complete or partial obsolescence of carina forks and special general shape.
52 PROCEEDINGS OF THE NATIONAL MUSEUM vol.68 in identifying the specimens depicted on plate 1 with Hinde's species. The carina from the branch to the lateral lobe leaves the main crest at an approximately right angle. It is thin inside, but the branch thickens towards the edge of the plate.
Characterized by the great thickening of the anterior part of the jaw-like plate and the swelling just below the denticles.
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EXPLANATION OF I'LATES
15, 16) Two specimens, illustrating the same side but right and left, show relationship to L. panderi, but differ in the return of the head tip and denticles. The specimens here illustrated are from the Rhinestreet Shale of Shaleton, N. Y., and the illustrations are enlarged 15 diameters. Two specimens, one (7) a form in the rock illustrating the short main point and the thick rod.
Two examples showing the wide angle made by the two ends of multiple denticles.
ART. 12 CLASSIFICATION OF CONODONTS ULEICH AND BASSLER 57
Bryantodus coale-scejis, new species 25 The type specimens showing the fusion of four or five. Two teeth showing the similarity in size of the main point and several of the teeth. Specimens illustrated here are from the Rhinestreet Shale at Shaleton, N.Y., and the illustrations are enlarged 15 diameters.
Two examples that show range in size, but both illustrate the characteristic long, straight, outwardly curved rod. Three teeth with the characteristic short, thick bar surmounted by few well-separated teeth. The specimens illustrated here are from the Hardin Sandstone Basal Member of the Mississippian-Chattanooga Black Shale at Mount Pleasant, Tenn.
Concave lower surface (1) and upper surface (2) of the type specimen. Ui)por surface of the type specimen (3) and under surface of another plate referring to the species. The samples are from the Hardin sandstone basal member of the Mississippian-Chattanooga black shale at Mount Pleasant, Tenn.
ART. 12 CLASSIFICATION OF CONODONTS ULRICH AND BASSLER 61
Section of jaw of a recent shark, X 2.5 and X 6, showing arrangement of teeth and their similarity to conodont genera such as Bryantodus. Outer and inner sides of the jaw of a recent myxiue fish {Myxine glutinosa) from Stonington, Connecticut, with an isolated tooth, showing resemblance to such conodonts as Distacodus.
