Anthessius — Illg 
$41 
fused. The antennule is 7-segmented. The an- 
tenna is $ -segmented, the basal 2 segments each 
with 1 seta, the terminal segment with several 
setae and several characteristic articulated hooks. 
The mandible is an unsegmented flat plate 
tapering apically in a long setiform process. An 
equally well-developed accessory process is arti- 
culated on the anterior margin just proximal to 
the distal lash. Marginal ornamentation is 
strongly developed in both elements. The max- 
illule is a flat plate, with expanded and some- 
what incised apical margin, with armature con- 
sisting of an articulated spine and seta. The 
maxilla has a greatly expanded basal segment, 
the flat apical segment tapering and bending 
anteriorly to form a heavily cuticularized ele- 
ment with right-angled outline, usually with 1 
accessory articulated spine or seta, and with 
the margin developed as a series of conspicuous 
spinous processes. The maxilliped of the female 
is obscurely 3 -segmented, with reduced arma- 
ture. In the male the maxilliped is 3 -segmented, 
the terminal 2 segments participating in a 
characteristic subchela. Hand of subchela in- 
flated and with ornamentation of spinules and 
spines. Finger of subchela very elongate and 
bearing accessory seta. Legs 1 to 4 biramous, 
all rami trimerous. Armature well developed, 
the most characteristic pattern being that of the 
terminal segments of the third endopodite, bear- 
ing 4 spines and 2 setae; that of the terminal 2 
segments of the fourth endopodite, bearing on 
segment two 2 setae, on three 1 seta and 4 spines; 
and that of the terminal segment of the fourth 
exopodite, this bearing 5 setae and alternatively 
3 or 4 spines. The fifth leg has 1 free segment, 
the basal element being only a setiferous prom- 
inence of the body segment. The flat, elongate 
free segment bears four elements of armature, 
characteristically 3 spines and a seta. The sixth 
legs are not particularly distinctive among those 
of poecilostomes, and the caudal rami are vari- 
able in proportions, although the typical cy- 
clopoid armature is consistently well developed. 
Sars designated Boeckia arenicola Brady as 
the type of Pseudomolgus. The type for An- 
thessius has not yet been fixed, but must be 
selected from one of the two original species 
of Della Valle, A. pleurobrancheae and A. sole- 
curti. On the basis of the redescription and ex- 
tensive illustration of A. solecurti by Stock 
(1959), this species is herewith designated as 
the type of the genus. 
Anthessius hawaiiensis (Wilson) 
Figs. 1-11 
Pseudomolgus hawaiiensis C. B. Wilson 1921. 
Type locality off South Coast of Molokai, 
Hawaiian Islands, "Albatross” Station 3853, 
type host Pleurobranchus sp. 
SPECIMENS EXAMINED: Wilson’s types were 
seen in the U. S. National Museum and were 
found to compare reasonably well with the habit 
figures he presented, although none were in good 
condition. A female paratype, USNM 53565, 
was dissected, and although some of the append- 
ages were lost in preservation and some in dis- 
section of the fragile specimen, a description 
was prepared to provide details for comparison 
with the species described below. Wilson used 
a different terminology for mouthparts from 
that now current, so his statements about the 
first maxilla refer to our mandible, his palp of 
first maxilla is our maxillule, but his second 
maxilla corresponds to our usage. His descrip- 
tion in general corresponds to the type speci- 
mens, but his illustrations are variable in reli- 
ability. The antennule and antenna are very 
generally depicted, without providing details of 
armature. The mandible is generally illustrated, 
although some details of the armature are lack- 
ing. The maxillule is inadequately depicted. The 
maxilla is presented in essential outline, but 
the detailing is somewhat misleading. He indi- 
cates more processes on the terminal segment 
than the type material corroborates. For the 
female, the first leg is essentially depicted, al- 
though the figure does not indicate completely 
the apical spine of the terminal segment of the 
exopodite. The second and third legs are illus- 
trated in essential rough outline. The illustra- 
tion of the fourth leg presents serious discrep- 
ancy from that for the male and from the type 
material. The exopodite is not depicted as pos- 
sessing on the terminal segment the 3 lateral 
and 1 terminal spines illustrated for the male 
and which I find on the paratypic female. The 
figure of the endopodite corresponds in rough 
essentials. The illustration of the fifth leg cor- 
