386 EEPORT OF COMMISSIONER OF FISH AND FISHERIES 



type from the first three. The four segments following the first or 

 basal one are straight, cylindrical, or slightly compressed, armed with 

 short spines, especially below and at the distal end, subequal in length 

 but decreasing in diameter to the propodus, which bears in each pair a 

 short, slightly curved and comparatively weak dactylus. The seventh 

 pair is only imperfectly developed in the young specimen figured, but 

 never quite attains the size of the sixth pair, which is the largest. 



The pleon is scarcely narrower than the last thoracic segment and 

 tapers but little to the fifth segment. The last segment is triangular, 

 with the sides but little dilated, and is pointed at the tip without grooves 

 or carinations. The uropods scarcely surpass the telson ; the basal seg- 

 ment has its inner angle long and spiuiform, extending the whole length 

 of the inner margin of the inner ramus and ciliated toward the tip ; the 

 rami are flattened, the outer elongate ovate, obtuse ; the inner with the 

 inner margin straight, the outer curved and emarginate near the tip. 

 Both rami and the posterior part of the telson are ciliated. 



Length lG-50 mm , breadth 7-25 mm ; color in alcohol light brown, darker 

 toward the head ; eyes black. 



Linnets description of Oniscus psora is too indefinite to be certainly 

 recognizable, and in using his trivial name I have followed the au- 

 thority of Liitken and others. Our specimens agree well with the de- 

 scription of 0. psora by O. Fabricius, and are undoubtedly identical with 

 that species, which he describes as infesting the cod. They appear to 

 correspond also with Bate and Westwood's figure and descriptions, al- 

 though those authors make no mention of Fabricius under JE. psora. As 

 Kroyer referred the species to its proper genus, I have adopted his name 

 as authority for the combination. 



The specimen figured was dredged in the summer of 1872, a little to 

 the northeast of St. George's Bank !, in latitude 42 11' north, longitude 

 67 17' west, in 150 fathoms, soft sandy mud with a few pebbles, and is 

 young, as shown by its size and imperfectly developed seventh pair of 

 legs. Adults may surpass the size of the figure, but the specimen drawn 

 was enlarged three diameters. Adult specimens were obtained from the 

 Provincial Museum, Halifax^ Nova Scotia, labeled as found on the cod, 

 and were probably from, the fishing banks of that region, or from the 

 Banks of Newfoundland. During the summer of 1879 a considerable 

 number of specimens were received by the Fish Commission through 

 the Gloucester fisheries, of which only a few are included in the table of 

 specimens examined. These specimens were parasitic on the cod ( Gadus 

 morrhua), and on the halibut (Hippoglossus). Specimens have also been 

 obtained from the skate (Raid}. Whiteaves records this species from a 

 halibut, on the north shore of the Gulf of St. Lawrence. Fine speci- 

 mens were obtained by Mr. N. P. Scudder from off Holsteinborg, 

 Greenland, in Davis' Straits !, parasitic on the halibut, and collected in 

 July and August, 1879. It extends to Iceland (Edw. et al.) ; the British 

 Isles (B. and W.); the North Sea (Metzger) ; Finmark (Sars), and Spits- 

 bergen (Miers). 



