INVERTEBRATES. 151 



The outer chamber is only partially preserved, but must have 

 measured from seven to eight inches in width when complete. 



Siphuncle small and situated near the dorsum. 



We have seen but a single specimen of this fine shell, which 

 was obtained from the upper beds of the St. Louis limestone at 

 Greencastle, Indiana, where it was associated with Temnocheilus 

 coxanum, Solenocheilus collection. Orthoceras, etc. 



Collector, A. H. Worthen. 



GENUS TEMXOCHEILCS. McCoy. 

 TEMNOCHEILUS SCOTTENSE. (sp. nov.) 



PL XXVH, Figs.3-3a. 



Shell of medium size, subdiscoidal, sides of the volutions 

 broadly rounded, dorsum nearly flat on the chamber of habita- 

 tion: and depressed convex on the remainder of the outer volu- 

 tion ; volutions about three and a half ; umbilicus wide and 

 deep, showing nearly the whole of the second volution; test 

 thin, and apparently without external ornamentation. The 

 outer chamber occupies nearly one-half the outer volution. 



Septa arching slightly backward on the sides, and separated 

 on the dorsum, by a space equal to about one-fourth the trans- 

 verse diameter of the volution. 



Greatest diameter of the specimen in hand, 3% inches; trans- 

 verse diameter of the chamber of habitation, 1% inches; dorso- 

 ventral diameter of the same ! 5 /i 6 inches. 



Position and locality: Warsaw beds of the St. Louis lime- 

 stone, near Winchester, Scott county, Illinois. 



No. 2587 of the Illinois State Museum. 



GENUS ASCOCERAS. Barrande. 



ASTOCERAS SOUTHWELLI. (sp. nOV.) 

 PI. XXVII, Figs. 2-2a. 



This rare species is represented by two imperfect specimens 

 only, the one figured being the most perfect of the two in hand. 

 This shows only the chamber of habitation, the form of the 

 septate portion, and the extremity of the siphuncle. 



