NORTH AMERICAN INDEX FOSSILS. 



Phylum. MOLLUSCA. 



(Continued.) 



Class CONULARIDA Miller and Gurley 



Paleozoic shells, resembling in general shape some recent ptero- 

 pods like Styliola but usually much larger, of varying form, and 

 with thicker walls. The shells generally bear transverse septa 

 toward the apical or posterior end. 



Their systematic position is doubtful and their relationship to 

 the pteropods is probably distant, that of a parallel rather than 

 a genetically related group. Cambric-Permic. 



Literature. 

 American Conularidse are described in faunal works — among which 

 those of Walcott (Bull. U. S. G. S., lo and 30, loth Ann. Rep. U. S. 

 G. S.) may be mentioned for the Cambric, Hall (Pal. N. Y., Vol. V., 

 Pt. II. and VIII. ) for the Devonic, and the volumes of the Pal. Ohio, 

 and Pal. 111. for the Mississippic and Carbonic. See also Ruedemann, 

 R., '* Note on the Discovery of Sessile Conularia " (^Am. Geol.y Vol. 

 XVII., pp. 158-165, Pis. VIII.-IX., and Vol. XVIIL, pp. 65-71, PI. 

 II., 1896). 



Artificial Key to the Genera (Including Pteropods). 



A. Shell chitinous VII. Urothcca, 



B. Shell calcareous I. 



I. Shell wall thin I. 



I. Cross section circular a. 



a. Spiral longitudinal striae present V. Coleoloides. 



a. Only faint growth lines present Styliolina. 



I. Cross section usually triangular, some varying to oval I. Hyolithes. 



1. Cross section rectangular , b, 



b. Shell large X. Comtlaria. 



b. Shell small (about I inch long) 5. Hyolithes quadricostatus. 



I. Shell wall thick 2. 



2. Cross section circular c. 



c. Annulations present IX. Tentaculites. 



c. No annulations present f. 



f. Shell made up of concentric cones VIII. Salterella. 



