STATE GEOLOGIST. 109 



233. Terebratula, sp ? 



Locality — Stone Island in Saginaw Bay. 



235. Atrypa, sp ? 



Large, very gibbous, with numerous radiating rii>s. 



Locality — Pt. au Gres. 



234. Spirifer Keokuk, var, Sail. 



The general aspect is of this variety. The principal points 

 are as follows : The valves are nearly equally convex ; the 

 mesial sinus of the dorsal valve is abruptly elevated, but 

 instead of being divided into four distinct plications, presents 

 but two, which are distinctly marked. The ventral valve 

 has a sinus, simple at its origin, but soon divided by a dis- 

 tinct plication, and in some specimens by two lateral ones. 

 Surface on each side of the mesial fold and sinus marked by 

 about 8 plications, the two adjacent to the mesial sinus and 

 elevation originating from a single one near the apex. No 

 striae are seen on the surface. 



The variety above is from the St. Louis limestone. 



Our shell bears also a close relation to S. rotundatus var. 

 planath, DeKonihck (PI. XIV, Fig. 2, and XVII, Fig. 4) It 

 is, however, a little more transverse than these figures, ap- 

 proaching in outline S. acuticostatus, DeKoninck. 



Locality — Grand Eapids. 



LAMELLIBRANCHIArA. 



201. Allorisma clavata, McChesney. 



The "flattened or slightly concave space extending like a 

 sinus from the beak to the base" of the shell is scarcely per- 

 ceptible in my specimens. From the Kaskaskia Limestone. 



Locality — Cheboyong Creek, Tuscola county. 



202. Allorisma, sp 1 



Bears some resemblance to A. sinuata, McChesney, from the 

 Kaskaskia Limestone, but differs thus: Not prolonged poste- 

 riorly, nor extremely gibbous ; beaks less than one third the 

 ' length of the shell back from the anterior extremity; ventral 

 margin but very slightly sinuate, and surfaces of valves 

 scarcely depressed; concentric Tidges not very strong 



In form and makings it resembles Lithodomus Jenkinsoni, 

 McCoy, (Brit. Pal. Rocks and Foss. PI. 3 F. Fig. 2). 



Localities — Grand Eapids, Stone Island, Great Charity Island.. 



203. Allorisma, sp? 



Allied to A. sulcata, Fleming (King, Permian Fossils, PI. XX. 

 Fig 5), "from carboniferous shales, Redesdale, Northumber- 



