279 



fine concentric striae ; band limited by linear carina <»n either 

 side, the concentric striae making an abrupl retral curve 



within. 



Found in the Pleurodictyum beds, chiefly as casts. 



Pleurotomaria itys, var. tenuispira, Hall, differs in tli«> 

 greater number of volutions (seven or more): greater ro- 

 tundity of the last two volutions; strong revolving striae, 

 coarser crenulations, and absence of revolving carina limit- 

 ing the "band." 



Found " in the shales of the Hamilton group, ai Hamburg, 

 shore of Lake Erie." ( Hall, type. ) 



Pleurotomaria capillaria. Conrad. (Fig. 209.) (Pal. 

 N. Y, Vol. V., Pt. II., p. 77, PL 

 XX.) 



Distinguishing Characters. — Tur- 

 reted spire, with four or more volu- 

 tions, rapidly increasing in size; 

 ventricose body-whorl, an angular- 

 ity on its upper side caused by two 

 or three prominent revolving ca- 

 rina 1 ; revolving and concentric Fig. S09. Pleurotomaria capO- 

 ° laria (after Hall.). 



striae. 



Found in the Strophalosia bed, on the Lake Shore 



(rare). 



Pleurotomaria planidorsalis. Hall. (Fig. 210.) (Pal. 

 N. Y., Vol. V., Pt, II., p. 82, PL 

 XXI.) 



Distinguishing Characters. — De- 

 pressed trochiform, sub-discoidal 

 spire ; su b-angular volutions, 

 rounded below; aperture straight 

 on upper side, somewhat rounded 

 below; strong revolving carina, 

 two-thirds distant from suture to 

 peripheral band ; similar carina on 

 the lower side; simple band; 



strong concentric striae. 



Fig. 810. Pleurotomaria plant- 

 dorsalis. An obliquely compressed 

 specimen, with spiral band ararly 

 obliterated (after Ball) 



