258 THE DEVONIAN OF MISSOURI. 



free, ventricose, rounded or scarcely angular below, somewhat flattened on the upper 

 side, marked by several ridges and shallow depressions on the upper and dorsal sides; 

 aperture somewhat longitudinally oval; peristome sinuate, with a deeper sinuosity on 

 the anterior margin. Surface marked by fine, transverse striae, which are strongly 

 undulated on the inequalities of the shell, and crossed by fine longitudinal or revolving 

 striae."— Hall, 1859. 



Remarks — Only a single fragmentary cast has come under observation. The general 

 shape of the specimen corresponds closely to the above species, and the dorsal side 

 exhibits the characteristic longitudinal ridges. Apex, surface striae, and character of 

 peristome not observed. Aperture probably longitudinally oval or subcircular. 



Horizon — Lower beds. 



Figured specimen No. 27515, Walker Museum. 



Platyceras cf. newberryi Hall 



Plate 69, figure 2 



1859. Platyceras newberryi Hall, Nat. Hist. N. Y. Pal., vol. 3, p. 333, pi. 63, figs. 14a-c, 



1861. 

 1913. Platyceras newberryi Ohern, Geol. Surv., Md. Low. Dev., p. 479, pi. 86, fig. 4. 



Description — Shell small, subdiscoidal, with about three volutions, the last one 

 expanding rapidly and becoming almost ventricose, the first two small and closely coiled; 

 aperture not well preserved, probably circular or transversely oval. Surface marked by 

 widely and irregularly spaced, transverse, sinuous plications. These are crossed by 

 closely packed, and regular longitudinal striations. 



Remarks — The one specimen present in the collection is fragmentary, but near the 

 apex a portion of the shell substance is preserved, which shows the surface markings 

 in fine detail. In shape there is a close resemblance between this specimen and P. 

 newberryi, but the surface ornamentation differs; the transverse plications being more 

 widely spaced, more distinct, and more sinuous than in the specimens figured by Hall. 

 The transverse ridges are lacking, although there is a suggestion of them in the plica- 

 tions, which on the lower part of the portion of shell adhering, become distinctly coarse 

 and lamellose. There is no suggestion of flattening in the preserved part of the shell. 



This specimen is evidently not identical with P. newberryi, although the general 

 shape and strong development of the longitudinal striae suggest a close relationship. 



Horizon — Lower beds. 



Figured specimen No. 27519, Walker Museum. 



Platyceras nodosum Conrad 



Plate 69, figures 3-6 



1841. Platyceras nodosum Conrad, Ann. Rept. Pal. N. Y., p. 56. 



1859. Platyceras nodosum Hall, Nat. Hist. N. Y. Pal., vol. 3, p. 473, pi. 115, figs. 1-6; 



pi. 116, figs. 1-4, 1861. 

 1913. Platyceras nodosum Ohern, Geol. Surv., Md. Low. Dev., p. 469, pi. 79, figs. 13, 

 14. 



Description — Shell of medium size. The dimensions of an average individual are: 

 Height 45 mm., diameter 25 mm. Spire depressed, consisting of three or four rapidly 

 expanding volutions. In cross-section the whorls present an oval outline, the upper 

 side convex, the lateral side also convex and obliquely inclined to the upper. Surface 

 marked with spinose nodes, having no definite arrangement. Original shell present 

 in one small patch shows transverse, strongly marked, sinuous lamellae. Character of 

 aperture and peristome obscure. 



Remarks — This species is represented sparsely in the lower beds, but somewhat 

 more abundant in the upper. In general the specimens are smaller than those from the 



