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PACIFIC SCIENCE, Vol. XIV, July I960 
specimen. It appears to arise from an inner 
portion of the base of the antennae. 
This species will be contrasted to Prional- 
pheus species under that form. It is superficially 
similar to Alpheopsis idio carpus Coutiere, a 
species that may be found to be in this genus 
when it is re-examined; the two species differ, 
however, even if the mouth parts should be 
found to be similar, in the biunguiculation of 
the dactylus of the third leg. Alpheopsis fissipes 
Coutiere, which may also be found to belong 
in this genus, differs in the number of articula- 
tions of the carpus of the second legs. 
The specific name refers to the number of 
articles of the carpus of the second leg. 
Prionalpheus sp. 
Fig. 2 
LOCALITIES: 1 female, nonovigerous, carapace 
length 2.8 mm., total length 5.6 mm., from 
Arue, Tahiti, in dead coral heads 5-10 ft. deep 
(BD-3); 1 ovigerous female, carapace length 
3.7 mm., total length 10.6 mm., from outer 
edge of fringing reef at Korolevu, Vitilevu, 
Fiji (BF-16); both collected by senior author. 
Tahitian specimen with one second and one 
third leg intact; Fijian specimen with only sec- 
ond legs intact. 
DESCRIPTION: Base of rostrum not demarked 
from curvature of anterior margin of carapace, 
tip of rostrum reaching to middle of first an- 
tennular article and bearing four setae; ptery- 
gostomial angle somewhat produced and acute, 
but not projecting as a definite tooth. 
Antennular peduncle short and heavy, with 
second article about as long as broad; stylocerite 
reaching almost to end of second antennular 
article; outer flagellum bearing numerous heavy, 
but not stiff, setae. Ventral lateral spine of 
basicerite acute but shorter than that of P. tri- 
articulatus; dorsal lateral lobe present; lateral 
spine of scaphocerite reaching to middle of third 
antennular article, rounded edge of squamous 
portion to end of second article; carpocerite 
reaching to end of antennular peduncle. No 
ventral spine anterior to labrum at bases of 
antennules or antennae. 
Left mandibles similar to that of P. triartic- 
ulatus except anterior awl-shaped tooth only 
twice as long as adjacent tooth, and posterior 
tooth not acute but rounded; anterior process of 
left mandible fitting into corresponding groove 
of right mandible. Maxillulae of more normal 
form, as shown in Figure 2e\ inner lobe bearing 
numerous strong, hooked setae. Maxillae sim- 
ilar in form to those of P. triarticulatus , but 
with posterior portion of scaphognathite more 
slender. First maxilliped with curvature of endite 
less uniform; exopodite bearing laterally a heavy 
setiferous bristle (broken in specimens); epi- 
podites greatly reduced. Second maxilliped with 
endopod composed of only three conspicuous 
articles, one being very short and sandwiched 
between the first and third; basal article more 
rectilinear than that of P. triarticulatus; penulti- 
mate article pear-shaped in outline, about 1.3 
times as long as maximum breadth, bearing 
numerous heavy spines; tip half-round in out- 
line, bearing six strong spines. Third maxillipeds 
similar in conformation to those of P. triartic- 
ulatus but with all three articles of endopod 
bearing heavy setae, the setae of last article 
being equal in length to article. 
First legs lacking on both specimens. Carpus 
of second legs with four articles bearing the 
ratio 10:2.6: 1.8: 4.4; chela somewhat longer than 
distal carpal article, fingers and palm subequal. 
Third legs with ischium unarmed; merus 4 
times as long as broad; carpus 0.9 as long as 
merus; propodus 1.2 times as long as merus, 
armed distally with few weak spines; dactylus 
biunguiculate. 
Telson 2.1 times as long as posterior margin 
is broad, 1.2 times as broad anteriorly as poste- 
riorly, lateral margins almost straight, posterior 
margin strongly arcuate; only one pair of dorsal 
spinules, located posterior to middle; inner pair 
of spines at posterior lateral margin half as long 
as posterior margin is broad. Only one tooth 
on basal article of uropod; distal shoulder of 
outer uropod armed with one strong lateral spine 
and three flanking spines each almost as long 
as lateral spine. 
DISCUSSION : Even without the first legs, these 
specimens may be distinguished with ease from 
P. triarticulatus. Among more readily apparent 
differentiating characteristics, this species has 
(1) margins of the rostrum which are con- 
fluent with the anterior margin of the carapace; 
