170 TWELFTH ANNUAL REPORT. 



Caiithocamptus nortluimbricus, var. americanus. (Var. n.) 



(Plate 0: Figs. 6—14, 20—22.) 



One of our mjpst common species is very near the English forra, 

 so near, in fact, that I dislike to remove it from it. A few points 

 of divergence, however, may be mentioned. 



The form and proportions are much like those of C. minutus. 

 The head is large and ends in a prominent bent beak. The anten- 

 nae are rather long and slender and have a well marked llagellum. 

 (Brady figures no flagellum). The palp of the antennule is as in 

 C. minutus. The mandibular palp is small. The first pair of feet 

 normal, rather small; all the other swimming feet with two-jointed 

 inner rami, save in the case of the male third foot. The fifth feet 

 are exactly as figured by Brady, save that there is a prominence or 

 tooth of the basal segment near the point of attachment of the 

 terminal joint which is quite long. The sensory area of the head 

 is oval and pointed. The male antenna has a long flagellum, not, 

 as figured by Brady, a very short one. The egg-sac is very large, 

 oblong. The animal seems to fall short of the size of the English 

 species, though measuring upwards of 0.65 mm. Our form is very 

 well distinguished from any other species. It is found in lake 

 Minnetonka, lake Calhoun, and elsewhere. 



Sp. 7. Cauthocamptiis minutus, Mueller. 



Monoculus stapJiTjUnus, jurine. 



L'anthocamptus minutus, lilljkborg, baird, sars, uljanin, brady, herricic. 



Canthocamptus staphylinus, claus, frig. 



Canthocamptus minutus, var. occidentalia, herrick. 



A well known species which has been frequently described and 

 seems quite circumpolar in its distribution. 



First mentioned from America in a paper by the writer in 1S78. 

 A pretty full description will also be found in the author's Types 

 of Animal Life. A very abundant species, frequent in muddy pools, 

 but somewhat variable in abundance. It may frequently be found 

 in great numbers in winter. 



Sp. 8. Canthocamptus illinoisensis, Forbes. 



( Plate 0. Figs. 1—5.) 



This robust and pretty species was first taken near Minneapolis^ 

 by Mr. A. W. Jones, a student of the University, who found it in 

 a peaty ditch. Forbes' description is appended. 



"Length 1 mm. Head and first segment united; five abdominal 



