Mollusks 19 A 



Creek at Bernard Harbour. 



Lymncea caperata Say (on the mud). 

 Aplexa hypnorum Lm-ne (on plants). 

 Valvata lewisii Currier. 



Lake near point Williams, Victoria island. 



Lymncea caperata Say. 

 Valvata lewisii Currier. 



Lake between point Williams and mount Arrowsmith, Victoria island. 

 Lymncea caperata Say. 



NOTES AND DESCRIPTIONS OF NEW FORMS. 



Genus Leda Schumacher. 



Subgenus Portlandia Morch. 



Leda (Portlandia) collinsoni, n. sp. (PL II, figs. 3, 4.) 



Shell small, inflated, slightly inequilateral, olivaceous in the young, tending 

 to a dark brownish tint in the adult, the periostracum strong, minutely evenly 

 vermiculately wrinkled all over; anterior end shorter, evenly rounded; posterior 

 portion with a rounded ridge extending to the posterior extremity where it forms 

 a rounded point, the shell being compressed above and below this ridge and the 

 margin below slightly incurved and retractively obliquely truncate; the basal 

 margin is slightly rounded; there is a small lanceolate impressed area in front 

 of the low, slightly opisthocoelous beaks, and a large one behind them, but there 

 is no circumscribed lunule or escutcheon; the interior is white, there is a large 

 triangular resilifer below the beaks and eleven anterior and eight posterior hinge 

 teeth; no indications of a pallial sinus appear on the specimens but the adductor 

 scars are large and conspicuous. Height of specimen 6; length 8.5; diameter 

 4 mm. Station 27s. , off Collinson point, Alaskan Arctic coast, in three fathoms, 

 sandy bottom. Many specimens. 



This is a remarkable little shell, quite distinct from its nearest relatives. 

 It is of the same general type as Leda (Portlandia) arctica Gray, but much 

 shortened up, smaller 'and more acute behind in proportion to its size. The 

 curious vermiculation of the surface is probably in great part if not entirely a 

 function of the periostracum. Catalogue Nos. 4150 and 4151 (Ottawa). Types 

 and co-types. 



Genus Pseudamusium H. & A. Adams. 

 Pseudamusium andersoni, n. sp. (PL II. figs. 7, 8.) 



Shell suborbicular, translucent white, extremely thin and fragile ; hinge line 

 straight, the ears subequal, the right anterior ear slightly convexly striated but 

 with no perceptible byssal notch or ctenolium; the right valve with a few faint 

 concentric undulations near the umbo, beyond that smooth, near the lower 

 margin concave and appressed against the margin of the opposite valve; left 

 valve more convex, equilateral, smooth, polished with a few faint irregular 

 radial markings near the base. Interior polished, the ligament very small. 



The soft parts in alcohol are small, greenish, the margin of the mantle with 

 very numerous small blackish eye spots, the gills and foot very small. 



