281 



Foniid 



in the soft Calcareous sliales, on the Shore 



of Lake Erie, at Eighteen Mile Creek.'' ( Hall. ) 



Bellerophon LEDA. Hall. (Fig-. 212.) (Pal. N. Y., Vol. 

 v., Pt. n.,p. 110, PI. XXHI.) 



Bistin^-uishino- Chnrncters. — Sub-globose outline, slightly 

 flattened on back ; ra|)idly ex})anding 

 body-^vhorl ; wide aperture ; abruptly 

 spreading peristome, broadly sinuate 

 and notched in front; reflexed inner 

 lip, extending in a callus over the pre- 

 ceding whorl ; strong revolving strijp, 

 alternating in size; finer, sub-equal, 

 thread-like, cancellating, concentric 

 stritP; narrow, flattened, or slightly 

 concave revolving band, usually marked by several fine 

 revolving strijv. 



Found in the shales below the Trilobite beds, and in the 

 Pleurodictyum beds (rare); Strophalosia bed, in Avery's 

 Creek, and on the Lake Shore (connnon, though usually com- 

 pressed) ; also in the Transition shales, twenty feet below the 

 Strophalosia bed, in Erie Cliff (rare). 



BeUerophon led a 



Class Pteropoda. Cuvieu. 



The pteropods, or sea butterflies, are pelagic 

 animals, often found in vast numbers swim- 

 ming near the surface of the water after dark. 

 Though frequently naked, a large number 

 bear more or less transparent shells, which 

 are very variable in outline. The shells are 

 often found in vast quantities on the ocean 

 floor, constituting " pteropod oozes. " 



The head of the pteropod is indistinctly 

 defined, the eyes are rudimentary, and the 

 foot is represented by two lateral fin-like or 

 wing-like appendages, near the head ; the 

 body is straight or variously inrolled. Fig. 

 218 shows a modern pteropod with shell. 



Fig. 213. Styliola recta. 

 L e s u e ur . Recent ( after 

 Adams, from Zittel). This is 

 a modern form, closely re- 

 lated to the most abundant 

 fossil species of our rocks, i.e., 

 StyUolina fissureUa. Hall. 

 (s7i) Shell ; (/) modified foot. 



