ISOPODS OF NORTH AMERICA. 431 



angle of the segment. In the fifth segment they are large and con- 

 spicuous and situated about the middle of the lateral margin. In the 

 sixth and seventh segments they are large and conspicuous and sit- 

 uated in the posterior corners of the segments. 



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

 large terminal segment, which has the posterior margin produced in a 

 large triangular median lobe between the large post-lateral expansions. 

 The peduncle of the uropoda is twice as long as wide. The branches 

 are of equal length and two and a half times longer than the peduncle. 



The first pair of legs are subchelate. The propodus in the male has 

 the inferior margin near the proximal end produced in a rounded 

 expansion, bearing three long spines. The inferior margin of the 

 dactvlus is furnished with spines along the entire margin. All the 

 other legs are ambulatory, with dactylus uni-unguiculate. 



ASELLUS TOMALENSIS Harford. 



Asellus tomalensis HARFORD. Proc. Cal. Acad. Sci., VII, Pt. 1, 1877, pp. 54-55. 

 RICHARDSON, Proc. IT. S. Nat. Mus., XXI, 1899, p. 856; Ann. Mag. Nat. 

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

 Harriman Alaska Exp., Crust., X, 1904, pp. 224-226; Proc. U. S. Nat. 

 Mus., XXVII, 1904, pp. 668-669. HOLMES, Proc. Cal. Acad. Sci. (3), III, 

 1904, pp. 321-323, pi. xxxvn, figs. 39-42. 



Localities. Tomales Bay, California; Lake Washington, Seattle. 

 The description of this form is given in the following concise 

 manner: 



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

 to the extremity of the peduncle of the lower. Flagellum of lower antennae 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 Asellus were collected by the Harri- 

 man Alaska Expedition at Lake Washington, Seattle. I have referred 

 them to the above species, being unwilling to describe a new species 

 of Axellux from a locality so close to that from which A. tomalensis 

 was found, when so little is known about A. tomalensis. Some of the 

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

 the type and only specimen of ^-1. tomalensis in the collection of the 

 California Academy of Sciences. The result of his comparison is 

 given in the following quotation from his letter: 



About the only difference that I am able to make out is in the fact that the inner 

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

 exdpodite, and that neither is armed with a tuft of hairs at the 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 themselves are perfectly 

 smooth. They show no evidence of having lost anything. The fact, how'ever, that 



