NO. 1404. PARASITIC COPEPOpS—CALIGID.E— WILSON. 627 



end; the other pair are situated at the posterior corners. The papilla? 

 are all about equal in size and each is furnished with three small setsi?. 



The abdomen is rather more quadrilateral than in the female, the 

 anal lamina? are larger, and their setf\? are nuich longer. 



The chief difference in the appendages is found in the usual enlarg- 

 ing of the second antennti? and second maxillipeds. The fourth leg-s 

 are also relatively larger and project ])eyond the tips of the set^e on 

 the anal papilhe, but their structure is the same as that in the female. 



Total leng-th 7.2mm. Length of carapace 4.85 ram.; width of same 

 4.75 nnn.; length of genital segment 1.35 nun,; length of abdomen 

 0.7 mm. 



Color as in the female. 



(/u'j>pfH//(>>tsl, generic name of its host.) 



Like the preceding species, this one was first described by Kroyer 

 and Milne-Edwards under the genus Caligux^ and was first recognized 

 as a true Lepeoj^Jdheirus hy Baird in 1850. 



Like norchnanni.l also it seems to be practically confined to a single 

 species of fish, the halibut, the few specimens obtained from other 

 fish having- probably been rubbed off' a halibut caught in the same boat, 

 as suggested by various authors. 



The National Museum collection includes lots numbered 8031, 12038, 

 12631, 12031, and 30014, all from halibut caught off Greenland, Iceland, 

 and Cape Ann. 8031 are type specimens from Shetland. 



LEPEOPHTHEIRUS EDWARDSI, new species. 

 Plate XXI; Plate XXII, tifr. 258; tigs. 1, 4a, 4b, 11, 81, 34, 39 in the text. 



Female. — Carapace ovate, widest posteriorly, long-er than wide. 

 Frontal plates distinct, strongly curved, not quite half the width of 

 the carapace. Posterior sinuses shallow, wide, and well rounded. 

 Median lobe three-eighths the entire width, squarely truncated pos- 

 teriorly, and projecting well l)ack of the lateral lobes. The latter are 

 short, blunt, and straight (fig. 244). 



Free thoracic segment of medium leng-th and about half as wide as 

 the genital segment, contracted anteriorly where it joins the carapace. 

 Genital segment slightly ol)ovate with g-racefulh' rounded sides and 

 angles, contracted to a verv short neck before joining the abdomen. 

 The latter is one-fifth as long as the genital segment, wider than long, 

 and tapering posteriorly. It is made up of a single joint which is cut 

 for one-third of its length at the anus. Anal papilla? small, wider than 

 long, with short and stout set;^?. Egg tubes nearly as long as the entire 

 body and as wide as the abdomen, each containing 75 to 80 eggs. 



Anterior antennt^ of medium size, and well armed with spines and 

 sette; posterior pair rather slender and strongly curved. 



All the other appendages are tither lamellate or furnished with 

 lamellie sonKMvhere m their structui*e. 



