GASTROPODA— STROPHOSTYLID&. 



687 



Apex strongly incurved, shell rapidly expanding, ventricose 

 and dorsal ly carinate ; aperture nearly circular. 



Oriskany of New York and Pennsylvania ; Decewville of Ohio. 



258. P. equilateralis (Hall). Mississippi. 

 Symmetrically expanding from incurved but not enrolled apex. 



Generally attached to crinoids. 



Keokuk of Iowa, Illinois, Maryland, Missouri ; Burlington of 

 Iowa and Missouri. 



259. P. lodiensis (Meek). (Fig. 972.) Mississippi. 



Fig. 972. Palceocapulus lodiensis. (After Meek, Pal. Ohio, II.) 



Symmetrical, with slightly overhanging but scarcely incurved 

 beak and strong dorsal fold from beak to base. (Type of genus.) 

 Waverly of Ohio. 



LXXVI. Orthonychia Hall. 

 Platyceroid shells with apex incurved but not enrolled, and 

 generally long, slender, though not symmetrical 

 body portion. A polyphyletic group. Devonic- 

 Carbonic. 



260. 0. subrectum Hall. (Fig. 973.) 



Devonic. 



Minute (and solid) apex, abruptly incurved ; 

 shell long and slender, nearly straight ; no plica- 

 tions. 



Onondaga of New York, etc. 



261. 0. formosum Keyes. (Fig. 974.) 



Mississippic. 



Elongate ; strongly and regularly curved, lower portion plicate. 

 Transitional to Igoceras. 



Kinderhook of Iowa ; Burlington of Missouri. Attached to 

 crinoids. 



FlG. 973. Orthony- 

 chia subrectum. 



(After Hall, Pal. N. 



Y.,V.) 



