Pacific Alpheids II ---- - BANNER 
199 
localities: One specimen at E-l-285; 1 
at E-l-611; 1 at E-l-617; 1 at E-l-648; 5 at 
E-2-382. 
Alpbeus arnoa sp. nov. 
Fig. 5 
type specimen: A non-ovigerous female, 
12.2 mm. long, collected on Amo Atoll, 
Marshall Islands, by R. W. Hiatt at station 
E-2-343. Only specimen known. 
description: Frontal region of carapace 
extending considerably beyond eyes. Ros- 
trum short, triangular, reaching about 0.5 the 
length of visible portion of first antennular 
article; dorsally bearing a strong and abrupt 
carina that extends to slightly posterior of 
gastric region. Orbital hoods rounded, some- 
what inflated, anteromedially extending into 
flattened area, at highest about equal in 
height to dorsal carina, laterally demarked by 
an abrupt groove from carapace which covers 
base of antennal peduncle. Orbitocarinal 
groove shallow and rounded; orbitorostral 
area flattened. 
Second antennular article slightly less than 
twice as long as broad, 1.5 times as long as 
visible portion of first article, 1.7 times as 
long as third article; diameter only 0.6 that 
of the first article. Stylocerite acute, with tip 
reaching almost to end of first article. Basi- 
cerite unarmed. Scaphocerite with lateral mar- 
gin strongly concave, spine heavy, somewhat 
blunt, reaching beyond end of antennular 
peduncle; squamous portion narrow and 
shorter, reaching to middle of third antennular 
article. Carpocerite reaching to end of sca- 
phocerite. 
Large chela subcylindrical, slightly taper- 
ing, entire, 2.8 times as long as broad, with 
the fingers occupying the distal 0.3. Dactylus 
arched and rounded, calcified and white dis- 
tally. Tip of fixed finger similarly calcified. 
Merus 0.37 as long as chela, with outer face 
1.8 times as long as broad; all margins un- 
armed, but inferior internal margin projecting 
into a low but strong extension. Chela with 
only sparse scattered setae. Small chela 3.5 
times as long as broad, with simple conical 
fingers occupying the distal 0.38. Carpus 
somewhat elongate. Merus slightly longer 
(about 1096) than that of large cheliped, 2.5 
times as long as broad, also unarmed. Chela 
bearing a moderate growth of setae on su- 
perior distal face. 
Carpus of second legs with the ratio : 10: 
21:8:7:11. 
Ischium of third legs bearing strong tooth. 
Merus 4 times as long as broad, armed with 
a strong acute tooth distally. Carpus unarmed 
except for poorly developed distal inferior 
tooth, 0.3 as long as merus. Propodus 3.5 
times as long as broad, 0.66 as long as merus, 
armed on inferior margin with five strong 
spines and five weaker spines. Propodus and 
dactylus with usual scattered sparse setae. 
Dactylus curved, simple, and well developed. 
Fourth legs of similar armature and propor- 
tions. 
Telson 2.4 times as long as posterior margin 
is broad, anteriorly 1.4 times as broad as 
posteriorly, sides with slight taper; anterior 
pair of dorsal spines 0.39, posterior pair 0.60 
of length posterior from articulation; distal 
lateral spines moderately strong; strongly 
arcuate distal margins armed with numerous 
short heavy spines. Outer uropod with strong 
lateral spine and with distal margin armed 
with numerous shorter spines in addition to 
usual setae. Inner uropod bearing eight strong 
spines on distolateral margin and numerous 
short heavy spines similar to those of the 
telson along distal margin. 
discussion: This species belongs to the 
Crinitus subgroup, and within the subgroup 
it appears to be most closely related to those 
other species with an extended dorsal carina, 
A. bucephaloides Nobili, A . longecarinatus Hil- 
gendorf, and A. parvus de Man. From the 
first two species it can most easily be dis- 
tinguished by the lack of spines on the carpus 
of the third legs. A. parvus lacks the armature 
of the carpus, like this species, but the con- 
figuration of the anterior margin of the cara- 
