FOSSILS OF THE KEOKUK GROUP. 525 



of the aperture on each side. Just outside of this 

 prominence the ventro-lateral sides of the outer whorl at 

 the aperture are a little flattened. The aperture is one- 

 fourth wider than the dorso- ventral diameter, and forms 

 about three-fourths of a circle, being deeply rounded on the 

 dorsal side, much flattened within, and angular, or appar- 

 ently abruptly sinuous at each inner lateral margin. Those 

 angles at the inner lateral margins seem even to have pro- 

 jected out somewhat, as in the Argontwfa gondola, of 

 Adams, though probably not to the same extent. The 

 lip is rather deeply sinuous at the middle of the dorsal 

 side; and the septa were moderately concave, and slightly 

 arched backwards on each side. (Siphuncle and finer 

 markings of the surface unknown.) 



Greatest diameter of the shell, about 3.75 inches; great- 

 est breadth (at the inner side of the aperture), 2.65 inches. 



As we have not seen the siphuncle of this species, we are not sure 

 that it belongs to the sub-genus Solenocheilus, but from its similarity in 

 several respects to the species we have described under the name 

 ca})a:c.' which apparently has a dorsal siphuncle, we are led to infer that 

 it probably possesses the same character. It differs from that shell, 

 however, specifically, in having its body whorl less rapidly expanding, 

 and without a depression along the inner side for the reception of the 

 inner whorls. 



The specific name was given in honor of Prof. JOSEPH LEIDY, of 

 Philadelphia. 



Locality and position Warsaw, Illinois; Keokuk division of the Low- 

 er Carboniferous series. 



ARTICULATA. 



GEXUS PHILLIPSIA, Portlock. 



PHILLIPSIA (GRIFFITHIDES) PORTLOCKII, M. and W. 



PI. 19, Fig. 6. 

 PhiUipsia (GriffitMdes) Portloclni. MEEK and WORTH EX. 1865. Proceed. Acad. Xat, Sci.. Phila., p. 268. 



ENTIRE outline sub-ovate. Cephalic shield sub-semicir- 

 cular, nearly twice as wide as long, moderately convex, 



