ISOPODS OF NORTH AMERICA. 



519 



Fig. 565.— Munidion 

 PARVTJM. Leg of 



SIXTH PAIR OF 

 ADULT FEMALE. 



X 20i. 



all the segraents they are in the form of petiolated processes. The 

 epimcra are large plates which occupy the whole of the lateral niaruin 

 of the segments. These plates are larger on the posterior segments 

 than on the anterior ones. 



The abdominal segments are all distinct. The first five are pro- 

 duced laterally in epimeral lobes, elongated and leaf-shaped, decreas- 

 ing in size gradually from the first to the fifth segments. These lobes 

 do not cover the dorsal surface of the abdomen, or 

 obscure the small terminal segment, which is visible 

 dorsally as a small rounded petiolated process. 



The pleopoda are five pairs of double-branched elon- 

 gated leaf -like appendages; the inner branches are 

 smaller than the outer. The uropoda consist of a 

 pair of biramous appendages, each with one large 

 outer and one small inner branch, similar in shape to 

 the branches of the pleopoda. 



The ventral side of the abdominal segments is keeled on the poste- 

 rior margin. The pleopoda and a))doniinal (»pimera are somewhat 

 carinated on both surfaces. 



The marsupium is bounded by five pairs of incubatory lamella^ the 



thii'd pair of which do not overlap in the median ventral line, so that 



a small opening is left into the incubatory pouch. The terminal lo})e 



of the distal segment of the first pair is very small, 



but well defined. 



The seven pairs of legs are all similar; the basis is 

 furnished with an extremely high expansion, the an- 

 terior end of which is twice as high as the other end. 

 The male has all the .segments of the thorax distinct. 

 The segments of the a])domen are fused into a single 

 piece. There is no indication of the coalesced seg- 

 ments on the lateral margins of the abdomen, these 

 margins being entire. The posterior portion of this 

 segment is narrower than the anterior portion, its 

 apex, however, being widely rounded. Its length is 

 about one and one-half times its greatest breadth. 

 Eyes are present. 



Only one specimen comes from the Straits of Fuca, 

 taken l)y the U. S. Bureau of Fislieries steamer ylM^/- 

 tross at a depth of 152 fathoms. l*arasitic on Munida quadrisjyina. 

 Type.—Q9X. No. 29096, U.S.N.M. 



This species is a ver}' much smaller one than the type species of the 

 genus described by Dr. Hansen, « being less than half the size of 

 Mimidion princejJS, The present species differs from the type species 

 in its much smaller size; in the relatively larger and differently shaped 



FK;. oOd. — M I'M DION 



PARVUM. Male. 



X 23. 



"Bull. Mus. Coinp. Zool. Harvard College, XXXI, 1897, pp. 115-117. 



