L'Sl 



Found"* * * in the soft Calcareous shales, on the Shore 

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



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

 V., Pt. II., p. 110, PI. XXIII.) 



Distinguishing ( haracters.— Sub-glob< >se outline, si igh 1 1 v 

 flattened on back; rapidly expanding 

 body-whorl ; 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 striae, 

 alternating in size; finer, sub-equal, 

 thread-like, cancellating, concentric fig. 212. Beiierophon ie<ia 



„ t T,, (after Hall). 



stria?; narrow, flattened, or slightly 



concave revolving band, usually marked by several fine 



revolving stria?. 



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 (common, though usually com- 

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

 Strophalosia bed, in Erie Cliff (rare). 



Class Pteropoda. Cuviek. 



The pteropods, or sea butterflies, are pelagic 

 auimals, 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. 

 213 shows a modern pteropod with shell. 



Fig. 213. Styliola recta. 

 Le sue ur. Recent i after 

 Adams, from Zitteli. This is 

 a modern form, closely re- 

 lated to the most abundant 

 fossil species of our rocks. i.e.. 

 Styliohna flsaurella. Hall. 

 i.s/i'i shell ; (7) modified foot. 



