338 
the cephalosome in the genus functionally in- 
cludes the segment of the first legs. However, 
the legs themselves seem to function as part of 
the metasomal series of legs. The anterior part 
of the segment on the ventral side is involved 
in the formation of a posterior termination of 
the oral region. Functionally, then, the transi- 
tion from cephalosome to metasome is strongly 
indicated £S intrasegmental. In none of the 
species I have studied does the separation of 
the segment of the first legs from the anterior 
region seem to involve as free an articulation as 
that between successive pedigerous segments, 
although a well-developed inflected interruption 
of the integument may provide a conspicuous 
anterior boundary for the element. In the para- 
typic material of A. navanacis this feature was 
found to vary, one female being found with a 
well-developed suture indicating the segmental 
boundary, a second female showing no interrup- 
tion of the integument. 
The structure and ornamentation of the anten- 
nule emerge as remarkably consistent through- 
out the species and it is strongly probable that 
a basic form as well as a characteristic ornamen- 
tation will be found consistently when details 
have been presented for all species. A very in- 
teresting dichotomy exists with regard to sexual 
dimorphism in the armature of this appendage. 
Bocquet and Stock were the first to point out 
the remarkable complement of aesthetes in the 
antennule of males of A. arenicolus and A. teis- 
sieri. As can be seen by comparing their findings 
and the descriptions below, there is apparently 
a typical distribution of aesthetes on the anten- 
nules of females, these occurring regularly on 
segments % 6, and 7. Bocquet and Stock de- 
scribed in the males of the species they studied 
this same complement of aesthetes with addi- 
tional aesthetes found on segments 2 and 4. 
Exactly the same pattern was found in the new 
species described below, A. lighti. However, on 
the basis of careful study of equally favorable 
material of A. nortoni and A. fit chi, both new 
species, I can say that no such dimorphism exists 
in these species. It will be of interest to see how 
this feature is found to be distributed among the 
species of the genus. Unfortunately the type 
material of A. navanacis available to me was not 
sufficiently well preserved to make possible de- 
PACIFIC SCIENCE, Vol. XIV, October I960 
termination of this feature, and for A. hawaii- 
ensis I could not find males. 
The antennae and the mandibles, maxillules, 
and maxillae are extremely similar throughout 
the species of the genus, so that a generic pattern 
might very soundly be said to exist, although 
there are minute details of specific variation. The 
maxillipeds, highly dimorphic in the sexes, are 
also somewhat more strongly specifically distinc- 
tive in details of ornamentation than are the 
other mouthparts. The swimming legs have a 
very consistent pattern of structure and orna- 
mentation throughout the genus, with, however, 
fairly distinctive specific features of outline and 
proportion of segments and of fine details of 
minute ornamentation. Two major alternative 
patterns of armature appear through the series 
of species, some having three spines on ; the 
terminal segment of the fourth exopodite, some 
having four spines there. In all the species below 
in which I have been able to study both sexes 
(four of the five), I have found a sexual dimor- 
phism of the first legs. On the terminal segment 
of the endopodite there is a spine and five setae 
in the female, two spines and four setae in the 
male. The species involved are sufficiently di- 
verse in their other variable characteristics that 
I would venture to predict on the basis of these 
that such dimorphism will probably be found 
consistently throughout the genus. 
The basic pattern of the fifth legs is consistent 
among the species, but there are distinctive 
variations in proportions and in the placement 
of the elements of the armature. There is a sexual 
dimorphism characteristically in this appendage, 
also, but the variation may be very subtle in 
degree in some species. Dimorphism of the 
caudal rami also seems substantially indicated, 
but for this feature additional investigation of 
the previously known species is required. Finally, 
with regard to sexual dimorphism it should be 
stated that in this group, where unusually large 
cyclopoid species are included, there is remark- 
ably little difference in size of males and females 
in many of the species. More information is 
needed on this feature, but the situation is par- 
ticularly striking in such a distinctive species as 
A. ft chi, described below, which is gigantic and 
equipped with strongly developed epimerae. The 
male is slightly larger than the female, which is 
