. 502 FAUNA CANADENSIS. 



16. EpTiemeridcB. 

 ' LarvJB of two or three species of Ephemerids were found rarely 

 in shallow water to a depth of two fathoms. 



MOLLUSCA. 



The Mollusca, though very abundant individually, and represented 

 by no less than twenty-one species, present no points of special inte- 

 rest, being all more or less familiar fresh-water forms. It is notice- 

 able however, that their bathy metrical range is not so wide as might 

 have been anticipated from previous researches. "With one excep- 

 tion, all the examples dredged from depths greater than perhaps four 

 or five fathoms were dead, and almost all the living individuals were 

 obtained from depths less than three fathoms. Valvata tricarinata 

 alone, was found in a living state in depths extending up to eight 



fathoms. 



17. Melania Virginica, Say. 



Shell tapering, elongated, with seven whorls above the body- whorl, 

 the whorls slightly rounded, and crossed by longitudinal curved 

 striae. Aperture sub-ovate, pointed above, its columellar margin 

 slightly thickened and callous. Colour reddish brown or olive, 

 without bands. 



Length from one quarter of an inch to one inch ; length of 

 aperture in lai-ge specimens nearly four lines. 



I at first thought this species might be only a variety of M. depygis, 

 Say ; but it appears on more careful examination to belong to M. 

 . Virginica. 



Hah. — Common in from two to three fathoms in Toronto Bay. 



18. Planorhis trivolvis, Say. 



Shell most readily recognised by the fact that it is carinated on 

 both sides, but most markedly on the right side, on which the 

 volutions of the shell form a depressed spire. The lip is thickened 

 internally, and is angulated opposite each carina. The whorls are 

 marked with curved transverse lines, and the general colour of the 

 shell is pale olive. 



JJab. — Yery common in shallow water, but not extending beyond 



three fathoms. 



19. PlanorMs, sp. 



A form allied to the preceding, but which I have been unable to 



; identify. It is distinguished from F. trivolvis, Say, by its much 



