Some Aoridae (Amphipoda: Gammaridea) Collected by the 
Hancock Expeditions to the Eastern Pacific, 1931-1941 1 
A. A. Myers 2 
ABSTRACT: New records for the Pacific are given for three species of Micro- 
deutopus Costa, one species of Acuminodeutopus Barnard, one species of Amphi- 
deutopus Barnard, and one species of Neomegamphopus Shoemaker. Full descrip- 
tions are given of Microdeutopus hancocki sp. nov. and Microdeutopus trichopus 
sp. nov. 
The parameters of the various families of 
"domicolous” Amphipoda have recently become 
particularly difficult to define owing to the 
discovery of numerous intermediate forms (Bar- 
nard, 1959, 1961 b, 1962, 1964). The Aoridae 
can be described most conveniently as species 
of the aorid-photid-corophiid complex which 
have the male first peraeopod (=:gnathopod) 
more markedly developed than the second, the 
urosome laterally compressed, and the third 
uropod with two, more or less subequal rami. 
The present paper deals with those genera of 
the family Aoridae in the Hancock collections 
in which the first male peraeopod has the car- 
popodite more bulky than the propopodite, 
with teeth on its posterior margin. 
I am indebted to Dr. J. L. Barnard and the 
United States National Museum for making 
the material available to me, to Dr. E. Naylor 
for helpful discussion, and to the Natural En- 
vironment Research Council for financial sup- 
port. 
Microdeutopus schmitti Shoemaker 
Shoemaker, 1942. Smithson. Misc. Coll. 101 
(11): 18-21, fig. 6 
Fig. la, d, j, l 
identification: Specimens agree well with 
the original description (Shoemaker, 1942). 
Figures of the paragnaths, ventral peraeon 
spines, and first and second peraeopoda are 
given for comparison with M. hancocki sp. nov. 
1 Allan Hancock Foundation Contribution No. 319. 
2 Department of Zoology, University College of 
Swansea, Swansea, Wales. Manuscript received August 
11, 1967. 
distribution: Present material came from 
Costa Rica, and was particularly abundant in 
the numerous samples from Salinas Bay. For- 
merly the species was recorded from Baja 
California and California, apparently reaching 
its most northerly point of distribution at 
Cayucos (Barnard, personal communication). 
Microdeutopus hancocki sp. nov. 
Figs, lb, c, e-i, k, and 6a 
identification: Among M. schmitti from 
Salinas Bay, Costa Rica, occur a few male 
Microdeutopus which differ constantly from the 
M. schmitti males in a number of characters. 
Unlike M. schmitti (Fig. Id) the first peraeo- 
pod (Fig. lb, c) has the basipodite greatly 
swollen antero-proximally, the carpopodite has 
a dentiform process on its anterior margin, and 
the propopodite has a single lobe on its pos- 
terior margin (cf. Fig. Id). In addition, the 
meropodite bears very long setae which are three 
to four times the length of those of M. schmitti. 
The second peraeopod has the carpopodite and 
propopodite approximately subequal in width 
at their junction and the propopodite is short 
(Fig. 1 h), whereas in M. schmitti the carpopo- 
dite is distinctly broader than the propopodite 
at their junction and the propopodite is rela- 
tively long (Fig. Ij). Also, the spine on the 
ventral surface of the sixth peraeon segment 
differs in the two types of male: that of M. 
schmitti (Fig. 1/) is well developed, though 
shorter than those of peraeon segments 3-5, 
while in present material (Fig. Ik) it is minute. 
Finally, the mandibular processes of the parag- 
nath are considerably longer in present mate- 
rial (Fig. 1/) than in M. schmitti (Fig. la). 
497 
