196 CRUSTACEA MALACOSTRACA. III. 



minal, somewhat short process projecting outwards and upwards, while a more proximal spine menti- 

 oned by Richardson is wanting; fourth joint agrees completely with the American description and 

 figure, as the joint is thicker than in P. hystrix, while the outer terminal tooth found in the last-named 

 species is quite wanting. - The only differences worth mentioning between my specimen and Richard- 

 son's description are two, viz. the absence of the spine on third antennal joint somewhat from its end, 

 and the end of abdomen which is only moderately emarginate. But judging from the variation observed 

 in P. hystrix these features have no significance as characters. 



Length of the single female 9 mm. 



Remarks. It may be mentioned that the marsupium contained female and male of the 

 Epicarid Clypeoniscus Meinerti Giard & Bonn. 



Occurrence. This single female was found in a bottle containing a number of specimens of 

 Arcturus Baffini and labelled: Iceland and the Faeroes. The contents were at least about fifty years 

 old. It was rather astonishing to find this species, known only from Alaska, in the bottle mentioned, 

 but there is not the slightest doubt that it was taken either at the Faeroes or, and perhaps more 

 probably, at Iceland; in earlier years our Museum did not possess a single specimen of any Isopod, 

 or perhaps even of any Crustacean, from Alaska. 



Distribution. Hitherto known only from Point Franklin, Alaska, i3'/ 2 fath. (Benedict). 



138. Pleuroprion frigidum n. sp. 



(PI. XV, figs. 7 a-; b). 



1901. Arcturus hystrix A. Ohliu, Bih. K. Sv. Vet Akad. Handl. Vol. 26, PI. IV, No. 12, p. 30; figs. 



6 a 6r. (Not A. hystrix G. O. S.). 



This species is in general aspect somewhat similar to A. hystrix, and has been confounded with 

 it by myself (1895) and by Ohlin, but on a closer examination it shows a number of specific characters. 

 Ohlin has figured both sexes, and his drawings convey a moderately correct idea of their general 

 appearance. 



Female. The spiniform processes as in P. hystrix, but on several segments of the body some- 

 what or much more numerous. The head has in its anterior row (fig. 7 a) four processes, the submedian 

 pair of very moderate length, the outer pair small. Each of the three anterior thoracic segments with 

 the normal transverse row. Fourth segment much longer than in the two preceding species, about 

 as long as the head and the three anterior segments combined, and armed with a great number of 

 processes of very different length, but seen from the side the long processes are arranged in four tole- 

 rably distinct transverse rows, while a fifth row with somewhat shorter processes is found between 

 first and second row, and many smaller spiniform processes are rather irregularly distributed, especially 

 on the sides. Each of the three posterior thoracic segments with its transverse row and, besides, with 

 several small sublateral or lateral spines. First abdominal segment (fig. 7 b) with only a single, curved 

 transverse row of six large processes, so that only one pair of submedian processes are found, but 

 these are very long. Last abdominal segment very different from that in either of the two preceding 

 species; each lateral margin (fig. 7 b) has a moderately large process conspicuously smaller than in 



