56 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxii. 



angle with the posterior margin, furnished with fewer siibniarginal 

 jspines than in the male; dactyl not strongh^ curved and litting the 

 palm closel}' . 



Posterior margins of the coxal plates of the third, fourth, and fifth 

 periBopods serrate. 



Postero-lateral angles of the first two abdominal segments slightly 

 produced, forming less than a right angle; the first two or three seg- 

 ments usually produced dorsall\% forming a well-marked median pos- 

 terior tooth. 



First uropods almost twice as long as the second pair; third pair 

 very short, not exceeding the basal segment of the second pair in 

 length; peduncle short, nearly as broad as long, furnished distally 

 with a few hairs; the single ramus slender, tapering, about equal in 

 length to the peduncle and provided with a few slender seta^ at the tip. 



Telson short, entire, as broad as long, and furnished distally with a 

 slender seta at each side. Length not exceeding T mm. 



Abundant throughout the United States. Collected at Caribou, 

 Maine; Cambridge and Quisset Fond, Massachusetts; Ann Arbor, 

 Michigan; Isle Koyal, Lake Superior; Wisconsin River, Lake Geneva, 

 Lake Delavan, and Winnebago Lake, Wisconsin; Omaha, Nebraska; 

 Urbana, Fekin, Clifton, Havana, McHenry County, Meredosia Lake, 

 and Lake Michigan, at South Chicago, Illinois; New Fhiladelphia and 

 Tuscarawas River, Ohio; Finey Branch, District of Columbia; Foint 

 Finellas, Florida; San Marcos, Texas; Lake Merced, Fresno, Los 

 Angeles, West Berkeley, and San Francisco, California; Yellowstone 

 National Park; Voh^an Reventado, Costa Rica. 



Through the kindness of Dr. S. J. Holmes, who has compared the 

 types of Bate's AUorchestes knickerbockeri in the British Museum with 

 specimens of Ilyalella dentata Smith, I am enabled to state definitely 

 that the latter are of the same species as Bate's types. From Bate's 

 description of Allorchestes knlckeThockerl in the Catalogue of Amphi- 

 podous Crustacea in the British Museum, one can not establish this 

 identity, for some of Bate's statements in this description do not agree 

 with his own specimens, and he has also confused the two sexes in his 

 figures of the gnathopods as well as in his description. Bate's speci- 

 mens were sent to him by Say under the name Gammarus minus Say; 

 but Say evidently misidentified his own species, for the specimens 

 which he sent to Bate, under the name Gaininarus tniniis Sa}^, agree in 

 no way with his description of this species. The specimens were then 

 des(;ribed by Bate as AUorchestes ktiickerhocherL The specific name 

 knickerhockeri has precedence of dentata^ consequently the name of 

 the species should be Ilyalella knickerhockeTi (Bate). 



In some specimens of this species the dorsal spines are absent on 

 the abdominal segments. These npndentate forms were first described 

 by Prof. S. I. Smith, and were given, the specific name inerinis. 



