694 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXXIII. 



The six free segments of the thorax are distinctly separated from 

 each other, are subequal in length, and are produced at the sides in 

 rounded lobes. The seven pairs of legs are prehensile. 



The abdomen is narrow, elongate, about twice as long 

 as wide, with all the segments completely fused. There 

 are no uropoda and no pleopoda. (See fig. 5.) 



The type from Station 4753 has Cat. No. 38527, 

 U.S.N.M. 



The fact that these Dajidse are found parasitic on 

 shrimps, decapodous Crustacea, and not on Schizopoda, 

 the hosts on which they have previously been found, 

 gives additional evidence, in respect to the relation of 

 host and parasite, showing that families founded on 

 such a basis, as well as genera and species, cannot be 

 maintained. Giard and Bonnier have arranged a classi- 

 fication of the Epicaridea whereby the families of para- 

 sites are restricted to certain orders of hosts, but Sars 

 has already pointed out the error of such an arrangement. The evi- 

 dence furnished herein proves that one family of parasite can infest 

 two different orders of host. 



Fig. 5.— Holo- 

 p h r y x u s 



CALIFORNIEN- 



sis. Male. 

 X 20i. 



ARTHROPHRYXUS, new genus.. 



Body of adult female irregular in outline, with lateral parts ex- 

 panded, and not projecting in front of the head. 



Head large and well defined from the thorax. 



The middle part of the dorsal surface of the thorax segmented 

 into five rather distinct segments. 



The abdomen is also distinctly segmented into five segments, the 

 terminal one being posteriorly triangular in shape. 



There are no uropoda or pleopoda. 



The oral area is small, rounded, but not greatly contracted behind. 

 The five pairs of legs are closely crowded together, and are bounded 

 by the five pairs of coxal plates. There are five pairs of incubatory 

 lamellae, the last pair being the largest, the two plates meeting along 

 the middle ventral line. 



The adult male has the head large, without eyes, the thorax com- 

 posed of six distinct segments, the first being fused with the head. 

 There are seven pairs of legs. The abdomen is indistinctly seg- 

 mented into about six segments, the last one of which is minute and 

 posteriori}^ triangular. The body is hunched and the abdomen con- 

 siderably curved under the thorax. 



There are no uropoda, and the pleopoda seem to be wanting. 



The type of the genus is Arthrophryxus bcringanus, the descrip- 

 tion of which follows: 



