TRopiDoi.EPTrs Fal'na at Canandaigia Laki:, N. W H'.i 



S. jiifiia Hall. Rare, one adult only. 



S. perplauii (Conrad). Common. Full series. 



Pholitiosfrophia iowa'ensis (Owen). Full series. 



Orthoihetes chemi/ngensis (Conrad). Common, full series. 



O. c/ic»iiiii:i:;e>!sis arctistriattis Hall. I'ull series. 



O. belliiliis Clarke. Full series. 



Chonetes coronatus (Conrad). Full series. 



Chonctes miicronatiis Hall. Full series. 



C. scitiiliis Hall. Full series. 



C. rolnistus Raymond. Full series. 



StropJialosia truncata (Hall). Full series. 



Prodiicfella spinulicosta Hall. Rare, all adults. 



Rhipidomella peiielope Hall. Rare, adults only. 



R. vafiiixenii Hall. Common, full series. 



Craniella hamiltoniae Hall. 



Hall, Pal. X. v., IV, 1867, p. 27, pi. 3, figs. 17-23. 



Crania crenistriata Hall. 



Hall, Pal. N. Y.. IV, 1867, p. 28, pi. 3, figs. 13-16. 



There are, among the shells froni Canandaigua Lake, about forty 

 dorsal valves of Craniella hainiltoniiB, the smallest of which is 3 mm. 

 long and 3.6 mm. wide. The largest is 15.2 mm. x 19 mm. One 

 specimen retains both valves, and there is a single imj)erfect ventral 

 valve attached to a specimen of Tropidoleptus. 



Nearly half of the specimens show by their strongly corrugated sur- 

 faces that they were attached during life to d^Tropidoleptiis, while others 

 show a variety of finer markings, or are entirely smooth. The young 

 shells are, as a rule, more conical than the adults. The smallest shell 

 has a height of i.66 mm. or .55 of its length. Another, 5 mm. long, 

 has a height index of .63. A specimen 6 mm. long has .52 for this 

 index : one 7.5 mm. long has .35 ; one 11 mm. in length has .27 and 

 the largest individual has .26. A itw of the small ones are, however, 

 quite depressed convex. One specimen, 4.16 mm. long has a height 

 index of only .32, while, on the other hand, the index of a specimen 

 12.33 mm. long is .44. 



The muscle scars show well in the dorsal valve, but add nothing to 

 what is known of them. A specimen 3.6 mm. long and 3.86 mm. 

 wide has the scars in the same relative position as in the adult, show- 



