LYMNJEIDJE OF NORTH AMERICA. 



141 



has a somewhat pinched-in appearance, and the body whorl is distinctly 

 shouldered; nuclear whorls 1*4, the texture resembling satin finish; 

 in outline the first part of the whorl is a small rounded knob about 

 one-fourth the size of the second part, which is wider than high; in 

 color it is shining yellowish-brown. (PI. XLIX, figs. A, B.) 

 Aperture 



Say's Type. 



Lake Ontario. 



Y. 



Niagara River, N. 

 Bear Lake, Mich. 

 Romeo, 111. 

 Pigeon Lake, Ont. 

 Lake Calumet, 111. 

 Erie Canal. 



Bitter Root River, Mont. 

 St. Lawrence River. 



Length. 

 42.00 

 40.50 

 50.00 

 49.00 

 47.00 

 41.00 

 46.00 

 46.00 

 57.50 

 49.00 

 43.50 

 46.50 



TYPE : Appressa; Academy of Natural Sciences of Philadelphia, 

 two specimens. Jugularis, types not in existance. 



TYPE LOCALITY: Appressa, Lake Superior; jugularis, original 

 locality not stated by Say. 



ANIMAL: Light or dark horn colored, tinged with bluish on the 

 foot; tentacles triangular, flat, rather long and tapering; foot short 

 and wide, truncated before and roundly pointed behind, 20 mill, long 

 and 9 mill, wide in an individual of ordinary size. 



JAWS (PI. VI, fig. A) : The superior jaw arched, very wide and 

 low, its cutting edge with a narrow, somewhat acute swelling in the 

 middle, with a larger, convex swelling on each side; lateral jaws some- 

 what triangular, the lower point of the triangle produced, long and 

 tongue-like, directed downward and outward when the jaws are pressed 

 out flat. The cutting edge of the jaws is very dark chestnut colored, 

 almost black in some specimens. The form of the superior jaw differs 

 considerably from the figures given in some European works, where 

 the lower median portion is shown as concave with a slight median 

 swelling. This may be due to the figure having been drawn from a 

 different position. Cooke (Moll., p. 211) figures the jaws as they 

 appear in the American specimens examined. 



RADULA: Formula (PI. VII, fig. A) 



( /-V* + * + + T + Y- + I + T 2 -V, 



(46-1-46). Central tooth with a single spade-shaped cusp; first to 

 nineteenth lateral teeth bicuspid; the mesocone very large, rather 



