FRESH-WATER CRUSTACEA OF THE UNU'ED STATES. 661 



Mr. Miliier has also collected at Ecorse, Mich., on the Detroit Eiver, 

 specimens probably of this species, but differing from the form above 

 described as follows: The flagellum of the antenuiilie contains one or 

 two more segments. The lateral portions of the head and segments of 

 the body, especially in fully adult specimens, are expanded so that the 

 outline of the animal is a broader oval. The open sinus in the lateral 

 margin of the head is a narrow incision, rounded at the bottom, but with 

 the sides sometimes meeting. The propodus in the first pair of legs is 

 uearl}' as much enlarged in the males as ia A. communis, and is armed on 

 its palmary margin with three acute teeth, of which the middle one is 

 the largest. 



I propose the variety-name dilata for this form, although inclined to 

 regard it as the more typical form of the species, which" was, however, 

 first described from the less perfectly developed specimens found in 

 Lake Superior. 



C^ciDOTEA STYGiA Packard. 



Americau Naturalist, vol. v, p. 751, figs. 132, 133, 1871 ; Fifth Annual Report Pea- 

 ''^' body Academy of Science, Salem, p. 95, 1873. 



Ccecidotea microcephala Cope, American Naturalist, vol. vi, p. 411, figs. 109, 110, p. 

 419, 1872, and reprinted in Third and Fourth Annual Reports of the Geological 

 Survey of Indiana, p. 163, 1872, (teste Packard;) Smith, American Naturalist, 

 vol. vii, p. 244, 1873. 



Found in Mammoth Cave, Kentucky ; Wyandotte Cave, Indiana; and 

 from wells at Orleans, Ind. 



I have had no specimens of this species for examination, but, as Pro- 

 fessor Packard suggests in his last paper, it is evidently very closely 

 allied to Asellus, and has no afiBnity with Idotea. Professor Packard 

 was at first misled by having only a single specimen and that one hav- 

 ing lost the caudal stylets. Professor Cope figures and describes his 

 specimens as having external "egg-sacs" attached to the tip of the 

 abdomen. These egg-sacs undoubtedly really belonged to some Ento- 

 mostracan, and probably to the parasite of the blind fish from the same 

 cave. Professor Packard says they were the caudal stylets mistaken 

 for egg-sacs by Professor Cope, but this seems impossible, as they are 

 figured and described as short, broad sacs filled with spherical bodies. 



B— THE CRUSTACEAN PARASITES OF THE FRESH-WATER 

 FISHES OF THE UNITED STATES. 



Scarcely anything has as yet been published upon the crustacean para- 

 sites infesting our fresh-water fishes, and the principal object of the 

 following partial synopsis is to call attention to the subject, and furnish 

 a basis for future investigation, which is of special practical importance 

 to all those engaged in raising fishes confined in ponds or other re- 

 stricted areas. 



The few species here enumerated are doubtless only a small fraction 



