382 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 112 



Some care must be exercised, since Hurley observed that some female 

 P. gracilipes have nearly smooth inner margins on the inner rami of 

 uropod 3; these margins are nearly smooth in North Pacific specimens 

 also. 



According to Hurley's diagnoses, the carpal process of P. gaudi- 

 chaudii P2 has several end spines, while that of P. gracilipes has one 

 stout end spine. The carpal processes of these species are shown 

 in figures lQa-b, looking down on the concave surface. Each 

 has one large, stout spine inserted near the distal end, and a series 

 of shorter, more slender spines distributed along the margins. The 

 carpal process of the large specimen of P. gaudichaudii has about twice 

 as many marginal spines as that of the small P. gracilipes, and the 

 process is longer in relation to its breadth. 



I have not seen any specimens of P. gaudichaudii from the North 

 Pacific, and it is included in this paper because of the possibility, 

 discussed under P. gracilipes, that Yamada's "Parathemisto sp. (12)" 

 may belong here. 



Distribution: As shown in figure 17, P. gaudichaudii is widely 

 distributed in the cooler part of the north Atlantic with a few scattered 

 records from warm water. Records in the southern hemisphere 

 are less complete than in the north Atlantic, but it probably occurs 

 throughout the Antarctic Ocean; i.e., the area between the Antarctic 

 Continent and the Antarctic Convergence (Sverdrup, Johnson, and 

 Fleming, 1942). 



Parathemisto (Euthemisto) libellula (Lichtenstein) 



Figures 16, d-o; 18; 19 



Gammarus libellula Lichtenstein, in Mandt, 1822, p. 32. 



Themisto libellula (Mandt), Stephensen, 1923, pp. 24-26, chart 5 [distribution]. — 



Shoemaker, 1926, p. 4; 1955, p. 72.— Dunbar, 1946; 1957 [biology]. 

 Euthemisto libellula (Mandt), Bovallius, 1889, pp. 281-283, pi. 12, figs. 1-31 — 



Sars, 1895, pp. 13-14, pi. 6, fig. 1.— Shoemaker, 1920, pp. 23-24, 28. 

 Parathemisto libellula (Mandt), Vinogradov, 1956, p. 211, fig. 10 [distribution]. — 



Barnard, 1959, pp. 123, 125, pis. 22-23. 



Diagnosis: The largest species of Parathemisto, reaching a length 

 of 60 mm. Body segments not produced into spines dorsally. Fe- 

 male antennae 1 and 2 subequal; antenna 1 slender, straight, lower 

 margin of flagellum serrate. First segment of mandibular palp 

 setiferous. Maxilliped with distal row of long setae on basal plate 

 and several long setae on lateral margins of outer plates. Carpal 

 process of P2 with short end-spine and rounded lobes behind the 

 spines on the lateral margins. P5 much longer than P6; P7 slightly 

 shorter than P6; dactyls of P5-7 strongly pectinate at their bases. 

 Inner ramus of uropod 3 serrate on both margins; peduncle strongly 

 produced at inner distal corner. 



