382 THE CANADIAN NATURALIST. [Dec. 



irregularly pitted, marked with more or less prominent, flexu- 

 ous longitudinal ribs, and bearing usually a rounded central 

 tubercle ; bordered in front, a little within the anterior margin, 

 by a wide, elevated, and rounded ridge ; posterior margin 

 having a similar but less conspicuous border. Length -3V inch. 



This species approaches very closely to C. ahyssicola Sars, and 

 C. Stimpsoni, Brudy. From the former it differs chiefly in having 

 a less pronounced marginal belt, a more rugged surflice, and a 

 less angular outline when viewed from above ; from the latter in 

 the absence of any sharply cut longitudinal crests, and by its more 

 rounded contour and elevated anterior margin. There is, however, 

 considerable diversity amongst the specimens here grouped under 

 the specific name Canadensis, and it is possible that a more ex- 

 tended series might have shown that they belong to two or more 

 species. The chief difference resides in the surface-ornament, 

 some exhibiting several short, rough and abruptly elevated ridges, 

 others being only moderately pitted, while some (from one of 

 which our drawings are taken) are intermediate in character, being 

 rather delicately ridged, chiefly on the posterior half, and vaguely 

 pitted and ridged in front. 



Cy there Dawsoni, nov. sp. (Figs. 8-10.) 

 Carapace, seen from the side, quadrangular, highest in front; 

 greatest height equal to half the length; anterior extremity 

 obliquely rounded, bordered with strong, blunt teeth ; posterior 

 narrower, rectangularly truncate, slightly rounded : superior 

 margin nearly straight, gently sloping backwards, irregularly 

 emarginate ; inferior almost straight. Seen from above, sub- 

 hexagonal; sides nearly parallel, suddenly tapering towards the 

 extremities, which are obtusely mucronate ; outline throughout 

 very rugged. Surface marked by irregularly scattered rounded 

 tubercles, and by two irregular longitudinal rows of transversely 

 elongated tubercular eminences. Length ts" inch. 

 This is apparently a very distinct species ; but the single speci- 

 men contained in these dredgings was unfortunately lost while 

 the drawings here given were in course of completion ; so that I 

 am unable to describe it as accurately as might be wished. 



Cytheridea elongafa, Brady. 

 The specimen so named is very doubtfully referred to this 

 species ; and the same remark may apply to 



Xestoleherls depressa, Sars, 



