Alpheid Shrimp — Banner 
153 
Antennular peduncle with second article 
1.7 times length of first article; third article 
subequal to first; second article 3.5 times as 
long as broad. Stylocerite assymetrically de- 
veloped, with that on left almost rounded 
anteriorly and reaching about 0.7 the length 
of first article; that on right anterior irregular 
(but rounded) reaching only a little more 
than 0.5 length of first article. 
Scaphocerite reduced to bract which reaches 
on left to end, on right to slightly beyond 
end of first antennular article. Basicerite un- 
armed. Carpocerite reaching 0.6 length of 
second antennular article. Antennal flagellum 
elongate. 
Large chela 2.7 times as long as broad, with 
fingers occupying the distal 0.2; margins 
mostly regular and strongly tapering. Distally 
chela with a deep pit proximal to articulation 
of dactylus to accommodate protruding mar- 
gin of dactylus; lateral and proximal to arti- 
culation of dactylus is located a shallow depres- 
sion with poorly defined margins. Fixed 
finger very short. Dactylus hammer-shaped, 
with distal margin swollen and rounded, 
proximal portion broad and thin. Carpus of 
usual form. Merus about 0.4 length of chela, 
with outer face 3.5 times as long as broad; 
distally unarmed; inferior internal and ex- 
ternal margins sharp; inferior internal margin 
bearing 13 slight and feeble spines. 
Small chela 5 times as long as broad, with 
the simple fingers occupying the distal 0.35. 
Merus 0.55 length of chela, 0.25 as long as 
broad, unarmed. 
Second legs assymetrical, with left as long 
as body, and right a little over half as long. 
Carpal articles of right legs with ratio: 
10:9:4:5:6; left leg with first article slightly 
shorter, relatively. 
Third leg with ischium unarmed; merus 
unarmed, 3.2 times as long as broad; carpus 
with distal angles rounded; propodus bearing 
3 single inferior spines and paired spines 
distally; dactylus simple and curved. 
Outer uropod bearing a single lateral spine 
without articulation, inner unarmed. Telson 
3.5 times as long as tip is broad, 1.8 times as 
broad anteriorly as posteriorly; sides slightly 
curved. Dorsal spines abnormal, with anterior 
left about 0.7 length posterior from articula- 
tion, posterior left located on margin; anterior 
right posterior to corresponding left, posterior 
right missing. 
DISCUSSION: This single specimen appears 
to be of the same species as the two frag- 
mentary specimens previously described but 
not named from Saipan (Banner, loc. at.). A 
number of slight differences are found be- 
tween the two forms : the length of the inter- 
orbital Carina, the proportion of the articles 
of the antennular peduncle, the ratio of the 
carpal articles of the second leg (only one 
second leg remained on the two Saipan speci- 
mens), the armature of the propodus of the 
third legs, and the proportions and armature 
of the telson. These differences, most of them 
in parts that have been found to be variable in 
T. idiocheles (Courtiere) and T. rathhtinae 
(Schmitt), as well as in related species of the 
Obesomanus group of Alpheus, are probably 
without significance. Another difference be- 
tween the two lies in the development of the 
antennal peduncle: in the male specimen from 
Saipan the scaphocerite reaches to the middle 
of the second article of the antennular pe- 
duncle, and the carpocerite reaches to the end 
of the same article, while in the female from 
Saipan the developement of these is shorter 
and more degenerate than that found in the 
male. As this male is similar to the Saipan 
female, the difference is obviously not sexual 
dimorphism, but may show the variability of 
the development of this appendage; however, 
the two Saipan specimens may be of different 
species. A final difference is found in the 
merus of the large chela, which in this speci- 
men bears 13 feeble spines, and in the Saipan 
specimen bears a few bristles in corresponding 
locations. Opposed to these slight and seem- 
ingly insignificant differences are many and 
great similarities, as can best be seen by com- 
paring the figures of the two forms. 
This species plainly belongs to Thunor if 
