NATURAL SCIENCES OP PHILADELPHIA. 429 



rapidly backward, forming along the middle belt a very deep, broad sinus. 

 Septa regularly concave. Young shell less angular in transverse section. 



Diameter of whorl (wholly septate) 2-4 (100) ; width of dorsum '92 (39) ; 

 dorso-ventral dimension '53 (22) ; number of transverse striae in one-tenth of 

 an inch, counted on the dorso-lateral angle, about nine. 



Locality. Marshall. 



The young shell of this species may be distinguished from the young of N. 

 striatulus, from the same group, by the presence of the transverse striae. 



Nautilus (Trematodiscds) altidorsalis, n. sp. Shell rather large ; section 

 quadrilateral, presenting an acute angle on the dorsum, a very obtuse one on 

 the ventrum, and an angle of about 80 on each side, about two-thirds the 

 distance from the dorsum to the ventrum ; sides of section but slightly curved ; 

 middle line of dorsum not seen. Septa with shallow concavity, somewhat 

 irregular a shallow sinus occupying the lateral carina, and another the dor- 

 sal, with a slight forward swell on the dorso-lateral slope, and another in the 

 umbilical cavity a very unusual arrangement of the sinuses, since the for- 

 ward sinuations are thus brought upon those points nearest the central line of 

 the shell. Surface marked by about 8 broad longitudinal grooves on the um- 

 bilical slope, and a large number on the dorso-lateral. Each of these grooves 

 contains about 18 very fine, wavy, raised striae. Both sets are crossed by fine, 

 somewhat irregular, transverse striae, nearly direct, though slightly sinuated 

 vent rally on the umbilical slope. 



Diameter of (completed) whorl wholly septate 2-1 (100) ; dorso-ventral 

 diameter of shell *67 (32) ; transverse diameter '78 (37) ; angle between plane 

 of whorl and dorso-lateral slope 48 ; between plane of whorl and umbilical 

 slope "55 ; longitudinal grooves in one-tenth of an inch 1| ; longitudinal striae 

 in same distance 30 ; transverse striae in same distance, counted on lateral 

 carina, 8. 



Locality. Marshall. 



This species, at first view, resembles N. strigatus, but is very distinct. Even 

 small fragments may be distingirished by the numerous very fine striae in the 

 grooves. 



Orthocekas, Breynius. 



Orthoceras multicixctum, n. sp. Shell small, very gradually tapering ; 

 section circular ; siphon central (?) ; surface marked by numerous small, acute, 

 transverse annuli, with intervening sharp grooves ; septa with shallow con- 

 vexity. Number of annuli in one-tenth of an inch 7. 



Localities. Marshall and Holland. 



A close analogue of O. cinctum, de Kon. (An. Foss. 512, xliii. 6, xliv. 5, 

 xlvii. 3), if it is not identical with it. The only perceptible distinction con- 

 sists in its smaller size and more acute annuli and grooves. O. cinctum is said 

 to occur in the Silurian, Devonian and Carboniferous systems. A species with 

 such tenacity of life may have had a great geographical range. 



Orthoceras gracilius, n. sp. Shell with an apical angle of 3 Q , a circular 

 section and central siphon. Cast smooth ; interseptal space "04 where the 

 diameter is -9. 



Locality. Union, Branch county, in argillaceous shales of the Huron group. 



Cythere, Miiller. 



Ctthere crassimarginata, n. sp. Carapace minute, ventricose, regularly 

 oval, microscopically wrinkled-scrobiculate ; hinge-line impressed, and hinge- 

 margin a little hollowed ; valves margined by a smooth bead, which projects- 

 slightly beyond the general surface, behind which is a small groove ; cast 

 smooth, but margined by a raised band terminating near the hinge anteriorly 

 and posteriorly. 



Length -08 ; breadth -05. 



1862.] 30 



