CAMBARUS. 97 



Gambarus virilis is subject to some variation in the shape of the rostrum, 

 the punctation of the carapace, breadth of areola, etc., as Hagen pointed 

 out in his account of this species, p. 64. Yet it is not liable to be con- 

 founded with any other species if good-sized specimens are at band. 



I have noticed in a few second-form (?) males of this species an inter- 

 esting variation from the ordinary type of the first pair of abdominal ap- 

 pendages. In most examples these appendages are split for a considerable 

 distance from the tip, and the two rami are drawn out to a point at the tip. 

 Tn the other specimens the whole appendage is stouter, the prominences 

 more pronounced, the extremity is split to a less distance from the tip, and 

 the ends of the rami are blunt, almost tubercutate. The hooks on the third 

 pair of legs are well developed, as in the first- form male. The abdominal 

 appendage is not articulated, but this is sometimes the ease in the other and 

 commoner type of abdominal appendage of the second-form males. I have 

 found both these forms together in collections made at several places ( Lake 

 Superior, Lake Winnipeg, etc.), and the differences in the sexual appendages 

 are not accompanied by any that would indicate a new species. 



A specimen of C. debiiis from Baraboo River, Ironton, Wis., sent by Mr. 

 Bundy, is the second form of the male of G. virilis. 



Males are occasionally found with small hooks on the third segment of 

 the second pair of legs, as well as on the third pair. 



From the U. S. National Museum I have received the types of Street's 

 ('. Gouesi and ('. virilis. The differences between the two are very slight, 

 and do not warrant their separation as two distinct species. Some of Hagen's 

 types of C. virilis from the Red River of the North and the Saskatchewan 

 Liver are of precisely the same form as Street's C. Gouesi. 



The following description of the living colors of G. virilis is given by Dr. 

 Streets from the notes of Dr. Coues on the specimens collected in the Souris 

 Liver, Dakota : — 



"Carapace variegated witli lighter and darker shades of brown: tail 

 segment darker and more uniform brown, with large, symmetrical, dark 

 brown spots, one on each side. Claws green, speckled with darker, with the 

 protuberances yellow and reddish; other legs paler greenish. Below, in- 

 eluding under side of the elaws. greenish white, the claws speckled with dark 

 spots. Antenna' rich brown." 



A large female specimen in the U. S. National Museum, collected by Mr. 

 Edward Palmer in a pond near Bridgeport, Jackson Co., Ala., appears to 



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