256 THE DEVONIAN OF MISSOURI. 



in the fauna by the depressed spire, the inclination of the upper side of the body whorl 

 toward the spire, and the obliquely sloping lateral sides which make, with the upper 

 side, a moderately sharp angle. 



Horizon — Lower beds. 



Holotype and Paratypes No. 27518, Walker Museum. 



Platyceras dumosum Conrad 



Plate 68, figure 5 



1840. Platyceras dumosum Conrad, Third Ann. Rept. Pal. Dept. N. Y. Surv., p. 205. 

 1879. Platyceras dumosum Hall, Nat. Hist. N. Y. Pal., vol. 5, pt. 2, pi. 14, pi. 5, figs. 

 11-16 and pi. 6, fig. 1. 



Description — Shell small, subovoid, consisting of about three whorls, the first two 

 contiguous, and the third or body whorl becoming free and expanding rapidly; spire 

 depressed below the plane of the body volution. Character of aperture obscure. Sur- 

 face marked by closely spaced, concentric, sinuous striae. At irregular intervals on the 

 longitudinal ridges there are projecting nodes which are extended into spines of uncer- 

 tain length. 



Remarks — One imperfect specimen may be referred to this Onondagan species. The 

 form is smaller than those figured in the New York reports and may possibly be an 

 immature individual. The spinose character of the surface is very distinctive of the 

 species. 



Horizon — Upper beds. 



Figured specimen No. 27527, Walker Museum. 



Platyceras elongatum var. parvum n. var. 

 Plate 68, figure 6 



Description — Shell erect, elongate conical, slightly curved, curvature near the 

 apex most pronounced. One or two curving undulations are present near the aperture; 

 aperture not fully preserved, but presumably sub-circular to circular in outline. Sur- 

 face essentially smooth. 



Remarks— One specimen only has come under observation. It resembles the young 

 specimen of Platyceras elongatum Hall, with the exception that the longitudinal and 

 transverse striations are absent. The curving undulations give the shell a twisted 

 appearance not noticeable in Platyceras elongatum, but such irregularities might be 

 considered as an accidental feature in growth, rather than a diagnostic specific char- 

 acter, and it seems best to consider this form as a variety of the above species. 



Horizon — Lower beds. 



Holotype No. 27525, Walker Museum. 



Platyceras gebhardi Conrad 



Plate 68, figures 7-10 



1859. Platyceras gebhardi Conrad, Nat. Hist. N. Y. Pal., vol. 3, p. 312, pi. 56, figs. 

 5a, 5b, 6, 7, 9; pi. 55, figs. 6a-b. 

 Description— Shell small, volutions expanding obliquely and rather rapidly. Spire 

 composed of three or four contiguous Volutions, apex in general plane of body whorl 

 or slightly below. Suture line deeply marked; aperture rounded or subovate, in some 

 specimens expanded. Surface finely striate transversely. The dimensions of an average 

 sized individual are: Height 13 mm., height of aperture approximately 11 mm.,' width 

 10 mm. 



