Bathyal Amphipoda — B arnard 
321 
Arctic. Pelagic. Minimum recorded depth 300 
m; minimum depth of closed haul 2200 m. 
family PLEUSTIDAE 
GENUS Mesopleustes Stebbing 
This genus stands directly between the Pleu- 
stidae and the Paramphithoidae, forming almost 
the perfect intergrade, but in reality it is better 
assigned to the Calliopiidae. The two former 
families differ only by the lower lip and coxal 
structure. The lower lip of the type genus 
Pleustes is composed of gaping, tilted, oval outer 
lobes astride broad partially fused inner lobes, 
whereas the lower lip of the type genus Param- 
phithoe is composed of two upright, ungaping 
outer lobes with distinct mandibular processes 
and no inner lobes. The first four coxae of 
Pleustes are broadly rounded below, whereas 
those of Paramphithoe are sharply acute below. 
The lower lip of Mesopleustes is composed of 
distinct outer lobes, slightly tilted, slightly gap- 
ing, with poorly developed but distinct mandib- 
ular processes and indeterminate inner lobes. 
The coxae are attenuated but not sharply acute. 
The simple mandibular molar of Pleustes in con- 
trast to the heavily ridged molar of Paramphi- 
thoe is of no consequence since other, undoubted 
pleustids have the paramphithoid molar. The 
slender gnathopods of Paramphithoe are imi- 
tated in other pleustid genera. Both families 
have species that are processiferous. 
The fusion of Paramphithoidae and Pleustidae 
is not necessarily warranted by this intergrading 
genus, for if the importance of lower lips were 
discounted then the Calliopiidae should also 
have to be included in the complex. The Callio- 
piidae scarcely differ from Eusiridae ( = Ponto- 
geneiidae) and a case could then be made for 
their inclusion with pleustids and paramphi- 
thoids. I do not advocate such extensive recombi- 
nation at this time in the Amphipoda, although 
the trend is obvious and, compared with other 
animal groups, the Amphipoda are certainly 
oversplit at the family level. 
Mesopleustes abyss orum (Stebbing) 
Figs. 4, 5 
Pleustes abyssorum Stebbing 1888:872, pi. 67. 
Mesopleustes abyssorum , Stebbing 1906:313; 
Chevreux 1927:92-93; Pirlot 1933:155- 
156; Schellenberg 1955:194. 
MATERIAL: Four specimens 22 mm, 22 mm, 
16 mm, and 15 mm, from Albatross Station 
5082, south of Hamamatsu, Honshu, Japan, 34° 
05' N, 137° 59' E, 662 fms, Oct. 20, 1906. 
REMARKS: The lower lip of three of the speci- 
mens has been dissected. None shows the false 
inner lobes drawn by Stebbing, and I believe 
those may have originated from pressure on the 
organ while mounted under a cover slip, for by 
compression with a needle at the inflated median 
line false lobes can be inflated where shown by 
Stebbing. Hence the lower lip is even less like 
that of pleustids and more like that of param- 
phithoids. 
Shallow pitlike thickenings of the chitin 
cover the body and the coxae and are drawn in 
enlarged figures. 
DISTRIBUTION: Previously recorded from the 
southern Indian Ocean, near Marion Island, 3013 
m; near Cape Noun, Morocco, 1180 m; NW 
Flores Sea, 694 m. 
family EUSIRIDAE 
GENUS Eusirella Chevreux 
Eusirella multicalceola (Thorsteinson) 
Figs. 6, 7 
Gracilipes multicalceolus Thorsteinson 1941: 
85-86, pi. 7, figs. 71-77. 
Eusirella multicalceola, Birstein & Vinogra- 
dov 1955:271, fig. 30; Birstein & Vinogra- 
dov 1960:224. 
MATERIAL: Figured female, 8.0 mm, and two 
other specimens, from Albatross Station 4758, 
off Queen Charlotte Islands, 52° 02' N, 132° 
53' W, 1600 fms, May 19, 1906. 
remarks : This species differs from E. elegans 
Chevreux (1908) by the much more slender 
gnathopods and the truncate first coxa, and 
from E. longisetosa Birstein and Vinogradov 
(I960) by the shorter third mandibular palp 
article, the much more deeply cleft telson, the 
shorter dactyli of the gnathopods, the shorter 
second article of the first maxillary palp, and by 
