The first radial parts are close to twice as long as the high woman, inform pentagonal, and cut all their width above to get the second radials. The body below the apex of the first radials is very depressed, nearly coiled in the plate, but concave below.
PROCEEDINGS OF
So-called pseudo-ambulacral fields rather narrow, somewhat convex, with mesial or ambulacral furrows rather wide and deep, especially above middle; pore or arm pieces, about twenty-two on each side of each area; lance-pieces very narrow but thick, and more deeply furrowed along the middle of that above, where they form the base of the ambulacral furrows; further down, the pore pieces close as almost or completely overlapping lancet pieces at the lower end. Elongate slits corresponding to the openings usually called ovarian openings in Pentremitcs, widest over the upper end and extending downwards apparently three-fourths of the length of the pseudo-ambulacral areas, so very close to the edges of the latter that they scarcely leave more than a thin space apparently not above and below ap. Along the margin of the pseudo-ambulacral areas are seen narrow, flattened, or very slightly concave spaces extending along the surface of the radial pieces and corresponding to the rather wide, deep furrows seen occupying the same position in the typical species, C. Column and pinnulaeunknown.).
Radial pieces one and a half times as wide, rather narrow below and widening upwards towards the middle, above which they are very slightly contracted to the top; each shared three-quarters of its length with its rather wide pseudo-ambulacral sinus. So-called pseudo-ambulacral areas* broad, moderately convex, tapering gradually below the middle and more abruptly above; so-called norepieces about 35 on each side of each area, less than half as long, across, as the width of the exposed part of the lancet pieces was at their widest part, almost across, but becoming somewhat oblique towards the lower part of the area; supplementary pore pieces small. Its ana- and interradial pieces are likewise decidedly smaller than in that species, while it also exhibits the marked difference of having its so-called ovarian apertures with each pair appearing on the surface as two closely approximated but distinct oblong-oval pores, rather than as a single round. , large opening.
Dance, however, differs not only in being much smaller and apparently more cramped in form, but in having much more deeply furrowed ambulacral areas and only six rows of interambulacral pieces at the widest part of the areas instead of eight, the plates also being large in proportion to the size of the body}'.
NATURAL SCIENCES OF PHILADELPHIA. 36
BRACHIOPODA
If, as we believe, it turns out to be a new generic type, we will propose the name hogramma. tiros, equal; }?*/*/*,alyn), in allusion to the remarkable evenness of the concentric lines of the surface. Shell attaining a rather large size, moderately convex, very transverse, or distinctly more than twice as long; greatest width on the hinge line; lateral limbs very attenuate and acutely pointed in young specimens, but become more obtuse in larger individuals. Abdominal valve regularly convex over the central region, and somewhat compressed towards the lateral limbs; mesial sinus begins narrow and very small near the bill, and gradually widens and deepens towards the front, where it is occupied by about eight depressed, rounded costa?, which, like those on the fold of the other valve, fuse with those on each side and with each other, to leave only one that extends. quite at the mouth;.
Surface ornamented by depressions, rounded, double or triple, costa more or less fasciculate, about five of which, on each side of sinus threads and. Towards the lateral extremities, about eight or ten smaller, simple, dark costae, not reaching the beaks, may also be counted, on each side of each valve, becoming gradually obsolete near the ends.
NATURAL SCIENCES OF PHILADELPHIA. 37 ing strife, and a few stronger marks of growth may be observed on well p
LAMELLIBRANCHIATA
NATURAL SCIENCES OF PHILADELPHIA. 1'J
Shell transverse, short oblong, very convex; posterior side broader than the other, and vertically subtruncate; anterior margin narrowly rounded;. Specimens from this latter locality are, in some instances, more depressed and oblique than the typical form from nearby Springfield, and they may perhaps belong to a separate species, if the differences observed are not due to accidental distortion. Shell small, about two and a half times as long as high, moderately convex, elongate rhomboidal outline; posterior border obliquely truncate so as to be angular at base; cardinal margin about three-fourths of the whole length, and nearly parallel to the base; anterior extremity very narrowly rounded; basal marginal straight at middle, but rounded very gradually upwards anteriorly; beaks compressed and placed about one-fourth of the entire length of the valves behind the anterior extremity; the posterior slopes of the hamstrings are subangular from the beaks sloping back and down, to the posterior basal extremity deeply rounded or subangular, while the spaces behind and above these slopes are compressed or slightly concave.
Surface marked by small ridges and growth lines, which are crossed by raised radius lines or linear arcuates, separated quite far posteriorly, but more closely arranged, and less strongly defined towards the anterior part of the valves. In the Proceedings of the Chicago Academy of Sciences of March 1866, p.17, we suggested that in the event the name Macrodon, Lycett, could not be retained for this genus, as it had previously been used by Mul'ler for the genus of fish, it could be called Parallelodon.
NATURAL SCIENCES OF PHILADELPHIA. II
Swaeltjie's species also occur in our Coal Mates, but we have only seen them from a higher part of the range, at Lasalle. Surface which appears to the unaided eye almost perfectly smooth, except very frequent, raised, concentric stria?, or small costres, on the anterior part of the valves, with obscure traces of smaller stria. However, when this layer is removed in this way, traces of the same mark can be seen on the surface of the layer below, with the help of a sufficiently strong magnifying glass.
The stronger concentric, raised striae, or small costas, visible on the anterior part of the valves, do not run exactly parallel to the very indistinct growth marks, but cross them obliquely. If you follow these little costae back to the shiny part of the valves, they all suddenly appear obsolete. Shield transverse oval, very thin, rather ventricose, equivalent valve, very scalene; beaks near the hind end and directed backwards; that of the right valve, the immediate apex of which bends under the beak of the left side.
Ashe does not suggest inequality of beaks, there are probably no specimens of the fossil species with two fused valves.
NATURAL SCIENCES OF PHILADELPHIA. 15
GASTEROPODA
It may differ, however, in having a much less convex periphery, and in having an outer whorl on the upper side, nearer to the outside, and also more wrinkled, owing to an apparent effort to form irregular knots. The true nodes around the visible part of its lower side are more numerous than in E. nodosus (which, instead of fourteen, rotate towards each whorl), and differ in being more irregular and almost obsolete on the posterior half of the outer whorl. Even if Montfort's name, Straparollus, is to be accepted for this genus, we believe that Sowerby's name, Euomphalus, should be retained in a subgeneric sense for those planorbicular species with angular whorls, such as E.
The shell attains nearly medium size, discoidal or subplanorbicular, concave, and shows all whorls both above and below, though the concavity is deeper below than above. At the junction of the upper side of the whorls, these lines begin, at first, almost at right angles to the suture, but curve a. Regarding the above, a single specimen was found, of the same size, and agreeing very closely with that from which the above description was drawn, but differing in being proportionately broader, and not so oblique in the periphery, which is also more convex in the middle.
Height of a specimen with apparently about two whorls on the top, and portions of the lower extremity of the produced body-fence broken away, 1-85 inches; width of body whorl, about 1-15 inches.
CEPHALOPODA
As it shows notracer, has an endrevolving band line, and has much the general physiognomy of subulites, however, concluded to refer provisionally to this group. The type of D'Orbigny's group was the Nautilusdorsalis of Phillips, which we think known only from a fragment showing the siphuncle to be marginal or on the outside of the curve like ammonites.* In this country we already know several Carboniferous species, that corresponds to the position of the D'Orbigny type in the position of the character or characters. siphuncle, and we find in all these another re-. But when we consider the further fact that the marginal position of the siphuncle in these shells is always accompanied by the peculiar character of the lip we have described, it becomes more important.
Circumference about one and a half, rapidly increasing in size and a little wider transversely than their dorso-ventral diameter; moderately extensive, subquadrangular in cross-section, the angles rounded, and the lateral and outer or ventral surfaces more or less flattened. The septa are moderately concave, about one-fourth the transverse diameter of the gyri at the point of measurement, and show a slight backward curve crossing the sides and margin.
NATURAL SCIENCES OF PHILADELPHIA. 49 by the breaking away of a thin part of the matrix between the uiphuncle and
Surface marked by rather well-defined lines of growth which curve slightly backwards into the sides of the whorls from the inner margin and make a stronger backward curve crossing the periphery to indicate the presence of a deep rounded sinus in the outer margin of the lip. It also appears to be related to If.tuberculatus of Sowerby, but differs from the published figures of this species in having its periphery proportionately wider and distinctly flatter; while its nodes are placed closer to the outer edge of the vertebrae, as well as more prominent. Danville, Illinois, from the shale above the fifth bed of coal, in the corrected Illinois section; to be near the horizon of the upper part of the Lower Coal measures.
Shell rather small, subdiscoidal, broadly rounded or depressed convex over periphery; umbilicus broad, rather deep, perforated and showing more than three-quarters of the dorso-ventral diameter of each internal whorl. One of these, which we consider the typical form of the species, has the periphery very depressed-convex, while in the other this part is distinctly more convex or rounded. The surface ornamented with several distinct, very regularly arranged costa?, which cross the sides of the turn very obliquely backwards from the inside, arc strongly backward as they approach the periphery, and after crossing the middle of the same, again arc forwards as on the opposite side , thus indicating a deep sinus on the outside of the lip; sinus very narrow, but not exactly angular at its termination, and widening rapidly forward; lived,.
Yet, as there is not the least appearance of any uncanniness of the revolutions, as in the genus Trochoceras, we have scarcely any doubt whether it is a true Lituit.
CRUSTACEA
In general it is more like L. Trocholitcs) ammonius, of Conrad, of the Lower Silurian, although it is.
NATURAL SCIENCES OF PHILADELPHIA. 53 Glabella rather depressed convex, wide anteriorly and narrowing posteriorly
Lateral lobes very narrow, evenly inclined from mesial on each side; bra? without furrows and with exposed surfaces he sees a twisted specimen that narrows laterally very quickly, with a strong curve backward; all more or less angular at the ends, the latter rather pointed; lappingsurfaces apparently wide. Its most marked characters appear Ofitseyes, and andhealmostantirire the absence of trilobation in Itshoraxand Pygidium, also the large egg of the same eye. Eyes large, forming an almost semicircular curve, with their posterior ends close to the posterior angle along the lateral edges of the head;
Surface of the internal cast of the entire upper part of the head without lines or grooves, but on the rostral shield clear transverse grooves are clearly visible. The rostral carapace also has a very different shape from that of Murchison's kind, being narrower in its antero-posterior diameter, and distinctly blunt rather than pointed at the lateral ends. Our species also shows no traces of the grooves on the cast of the top of the head, so strongly marked in /.
It is flat below and has a weak, undefined, blunt longitudinal ridge along the middle, with an equally undefined, shallow sulcus on each side between this and the lateral margins, which are sharp.
56 PROCEEDINGS OF
B. MEEK
