ISOPODR OF NORTH AMERICA. 481 



iin(>lo of tho segment. In tli(> ril'tli seg-nieiit they Jire lai'o-e and con- 

 spicuous and situated al)out the middle of the lateral margin. In the 

 sixth and seventh segments the}' are hii'ge and conspicuous and sit- 

 uated in th(^ ])osterior corners of the sc^gnients. 



The abdomen is composed of two short segments, followed by the 

 large terminal segUKMit. whicli has the posterior mai-gin produced in a 

 large triangular median IoIh' betwecMi the large post-lateral ex[)ansi()ns. 

 The p(HluncIe of the uropoda is t\vic(» as long as wide. The branches 

 are of ecjual length and two and a lialf times longei- than tiie peduncle 



The tirst pair of legs are subcludat(\ The ])rop()(lus in the male Iia> 

 the inferior margin near the ])ro\imal end })r()duced in a rounded 

 expansion, t)earing three long spin(vs. The infiM-ior margin of the 

 dactylus is furnished with spines along the cntir(> margin. All the 

 other legs are ambulatory, with dactylus uni-unguiculate. 



ASELLUS TOMALENSIS Harford. 



^Ixelliis Uniuden.sit: Hakfokj). rroc. Cal. Acad. Sci., Vll, I't. i, J<S77, pp. .54-.1.5. — 

 Richardson, Proc. V. S. Nat. Mus., XXI, 1899, p. 856; Ann. Mag. Nat. 

 Hist. (7), IV, 1899, p. 322; American Naturalist, XXXIV, 1900, p. 297; 

 Harrinian Alat^ka Plxp., Crust., X, 1904, pp. 224-226; Proc. V. S. Xat. 

 Mus., XXVII, 1904, pp. 668-669.— Holmes, Proc. Cal. Acad. Sci. (3). ill, 

 1904, pp. 321-823, pi. xxxvn, tigs. 39-42. 



Local'iflrx. — Tomah^s Hay, California; Lake ^\'ashinJ4ton, Seattle. 

 The desci'iption of this form is given in th(> following concise 

 manner: 



Head a little transverse, narrower than the body. Upper antenna not reaching 

 to the extrenuty of the peduncle of the lower. Flagelluni of lower antennfe longer 

 than its peduncle. Body narrow in front, gradually increasing in width toward the 

 tail. Peduncle of caudal appendages more than half the length of the terminal fila- 

 ments. Length .[\^ inch. 



The description is from a single specimen. 



Eight specimens of a species of AseUu>< were collected by the Harri- 

 nian Alaska Hxpi^dltion at Lake Wasliington, Seattle. T have referred 

 them to th(> above species, being luiwilling to descril)e a new species 

 of A-^eUns from a locality so close to that from which A. tomalensw 

 was found, when so little is known about ^1. f<)iii<il<msif<. Some of the 

 specimens were sent to Dr. William E. Ritter for comparison with 

 the type and only specimen of .1. foiiuilenyts in the collection of the 

 California .Vcademy of Sciences. The result of his comi)aris()ji is 

 given in the following (juotation from his letter: 



About the only difference that 1 am al)le to make out is in the fact that the inner 

 ramus of the sixth pleopods (uropods?) of A. tonialensis is about half as long as the 

 exopodite, and that neither is armed with a tuft of hairs at tlie tip. This is the case 

 with the one appendage present, but its mate is gone. It is possible that the hair 

 tuft may have been broken off, but the tips of the rami then^selves are perfectly 

 smooth. They show no evidence of having lost anything. The fact, however, that 



