ISOPODS OF NOKTH AMERICA. 



169 



Parasites of skate, cod. and halibut; on Gadus ogac,' on Myxo- 

 cephahis scorpius' on Soiiinlosuti inlcrocepJidhix; on Gach(f< caUarias. 



Body ovate, a little more than one and a half times longer than 

 broad, 10 mm : K! nnn. 



Head two and a half times broader than long, 2 mm : 5 nun. Ante- 

 rior margin widely rounded, and produced in a small median point, 

 which does not arch over the antennae to meet the frontal lamina on 

 the other side. Eyes large, oval, composite, occupying a largt; part of 

 the dorsal surface of the head, but not contiguous, although very close 

 together. The first pair of antenna? have the lirst two articles very 

 much enlarged; the lirst article is wider and longer than the second; 

 the second is produced at the upper distal angle in a process which 

 extends half the length of the third article; the third article is very 

 narrow, half as wide as the second article. The Hagellum is composed 

 of fourteen articles. The tirst antennge extend to the end of the 

 peduncle of the second pair of an- 

 tenna?. The first three articles of 

 the second antennae are subequal; 

 the fourth and fifth are a])Out equal 

 in length, and each twice as long as 

 the third. The flagellum is composed 

 of fifteen articles. The second pair 

 of antenna^ extend a little beyond the 

 posterior margin of the first thoracic 

 segment. The frontal lamina is large, 

 with base somewhat quadrate in 

 shape, with rounded angles, and ven- 

 trally placed, not dii-ected anteriorly. 

 The maxilliped has a palp of five 

 articles. 



The first three segments of the thorax are longer than the three 

 following. The seventh is very short, being only less than half as 

 wide as the sixth. The epimera of all the segments are distinct with 

 the exception of the first. They are narrow i)lates with the posterior 

 angles produced in the last four, although in the epimeron of the 

 fourth segment, the posterior angle is rounded. On all the epimera 

 there is a faint carina extending obliquely across the surface. 



All six segments of the abdomen are distinct. The first is com- 

 pletely covered in the middle by the seventh thoracic segment but is 

 visible at the sides. The lateral parts of the segments are not sepa- 

 rated oil' from the dorsal portion. The sixth or terminal segment is 

 triangulate, with apex not produced. The branches of the uropoda 

 do not extend beyond the tip of the terminal abdominal segment. The 

 basal segment extends tw^o-thirds the length of the sixth abdominal 

 segment. The branches are about equal in length, the outer one being 



Fig. 148.— ^ga psora (After Harger). 

 a, Ventral view, b, Dorsal view. 



X 3. 



