AMPHIPOD GENUS PARATHEMISTO BOWMAN 379 



1924 and Pirlot, 1939). Bary (1959) showed a similar difference in tem- 

 perature preference in southern New Zealand waters. The absence 

 of P. gracilipes from the Atlantic coast of the United States results 

 from the rapid change of temperature over the range inhabited by 

 P. gracilipes so that it literally has no living room. Hurley (1955) 

 pointed out that P. gracilipes inhabits more neritic water than P. 

 gaudichaudii in the New Zealand area, and Bary's (1959) detailed 

 analysis confirms this view. In the north Pacific the occurrence of 

 P. gracilipes in the east China and Yellow Seas may reflect its pref- 

 erence for coastal waters. Both of these seas are shallow and subject 

 to much runoff from rivers. 



In the vicinity of Plymouth, England, P. gracilipes undergoes a 

 diurnal vertical migration; it moves close to the surface at night and 

 descends during the day (Russell, 1925). Bary's data show evidence 

 of a similar migration in New Zealand waters. 



Parathemisto (Euthernisto) gaudichaudii (Guerin) 



Figures 16,a; 17 



Themisto gaudichaudii Guerin, 1825, p. 774. 



Themisto compressa Goes, Stephensen, 1924, pp. 103-110, figs. 43-49. 



Euthernisto compressa (Goes), Chevreux, 1935, pp. 191-192. 



Euthernisto bispinosa Boeck, Chevreux, 1935, p. 191. 



Themisto gaudichaudii Guerin, Stephensen, 1933, pp. 63-64; 1944, pp. 10-12; 1947, 



pp. 76-77; 1949, p. 54.— Pirlot, 1939, p. 39. 

 Parathemisto (Euthernisto) gaudichaudii (Gudrin), Barnard, 1930, p. 420; 1932, 



pp. 280-282 (synonomy).— Hurley, 1955, pp. 161-164, figs. 159-174. 

 [?] Parathemisto sp. (12) Yamada, 1933, p. 8, pi. 2, fig. 12, a-e. 

 Euthernisto antarctica (Dana), Ealey and Chittleborough, 1956, p. 22. 



Diagnosis (slightly altered from hurley, 1955): Length of 

 adult, 7-25 mm. Strong dorsal spines in animals of more than 10 mm. 

 total length. Carpus of P2 extends three-fourths along propodus. 

 P3 male carpus widest proximally, width nearly one-half the length; 

 like P. gracilipes, but rather more spines on surface and margin; 

 carpus and propodus subequal. P4 male carpus oblong-ovate, width 

 slightly more than one-half the length, fringe of small even bristles 

 on posterior margin; about 12 strong spines. Uropod 2 outer ramus 

 about three-fifths length of inner. Uropod 3 outer ramus two-thirds 

 length of inner; inner ramus with smooth inner margin; inner margin 

 of peduncle entirely smooth. P3 female carpus oblong-ovate and 

 widest proximally, width about two-thirds the length; numerous fine 

 surface spines, 10 marginal spines, marginal bristles throughout. 

 P4 female has about 18 surface spines on carpus. 



Remarks: As Hurley has pointed out, the most dependable cri- 

 terion by which P. gaudichaudii can be identified is the completely 

 smooth inner margins of the peduncle and inner ramus of uropod 3. 



