82 NORTH AMERICAN 



in width, first distinctly narrower than the contiguous elytra ; surface feebly 

 convex, coarsely, very closely, and evenly pnnctulate ; transverse carinae 

 tricuspid, middle cusps long, becoming finely acicular at tips, lateral broad, 

 short, widening at apex. Legs moderately long and slender, black above, 

 piceous-black beneath ; first joint of the posterior tarsi twice as long as the 

 second, as long as the fifth, second and third sub-equal, fourth short and 

 oblique, fifth very slender. 



Male. — Posterior edge of the fifth ventral segment feebly emarginate in its 

 middle fourth, emargination evenly rounded, twelve to fifteen times as wide 

 as deep, contiguous surface feebly and cylindrically impressed throughout 

 anteriorly; sixth segment sinuate at apex, sinus small, equal in width to 

 the vertices, somewhat more acute in curvature at bottom, about twice as 

 wide as deep. 



Female. — Sixth segment rounded behind. 



Length 2.9 mm. 



California, 2 ; Lake Tahoe, Nevada, 3 ; Lake Quesnel, British 

 Columbia, 1. 



Subdivision 8. 



Group III. 



The distinguishing feature of this small group is the minute size of 

 the species, which enter it, they having 2 mm. as a maximum limit 

 of length. It may be considered unnatural to constitute a group upon 

 the quality of size alone, but as this serves to identify them readily, 

 it is adopted for convenience. 



The following table shows the arrangement assumed for our three 

 species : — 



Transverse carinae of abdomen not cusped. 



Head as wide as the elytra. Lake Superior to Massachusetts. 



63. pusio. 

 Head narrower than the elytra ; more robust ; elytra relatively longer and 



more rectangular. British Columbia 64. iiamiliis. 



Transverse carinae tricuspid ; form much more slender... 65. atoiuarius. 



63. S. pusio n. sp. (Schwarz MS.). — Form robust. Pubescence short, 

 fine, sparse, setiform, cinereous. Head robust, twice as wide as long ; inter- 

 ocular surface nearly flat, more than twice as wide as the eye, somewhat 

 finely, very closely, and evenly punctate ; punctures closely crowded, slightly 

 polygonal in outline ; longitudinal elevation narrower than the lateral por- 

 tions, strongly and evenly convex, prominent ; ocular lines meeting at one 

 length in advance ; antennae scarcely as long as the width of head, rather 

 robust, piceous-black, club prominent ; third joint one-fourth as long again 

 as the fourth, joiuts three to five uniformly decreasing in length, six and 

 seven oval, eighth globular, narrower than the seventh, joints nine and ten 

 broader than long, last as wide as long, feebly acuminate; maxillary palpi 



