Alpheid Shrimp, X: Fiji, Tonga, Samoa — Banner and Banner 
175 
cerite degenerate, triangular, acute, with tip 
reaching only slightly beyond end of first 
antennular article; carpocerite reaching to past 
middle (in type) or to near end (in para- 
type) of second antennular article; flagellum 
about 6 mm long. (In both specimens the 
antennal peduncle and most of the scaphocerite 
are carried under the antennular peduncle, and 
so they are not fully visible in dorsal view.) 
Large cheliped lost in both specimens; small 
cheliped present only on type. Merus unarmed, 
slender, 4.3 times as long as broad; carpus 
slender; chela 5.0 times as long as broad, 
slightly curved; fingers slender, tapering to 
acute tips, 0.4 as long as chela; setae on appen- 
dage short and scattered. 
Second legs asymetrically developed, with 
merus of the right only 2.4 mm long, that of 
the left 4.0 mm long (0.5 mm longer than 
carapace). Carpal articles of left leg with ratio: 
10:12.5:4.5:5.0:6.5; of right leg: 10:14.8: 
43:5.0:6.7; on the remaining one leg of the 
paratype (evidently the longer leg): 10:17.2: 
4.4: 6.4: 6.8. Ischium strongly curved (almost 
broken on larger leg), merus with slight proxi- 
mal curving. 
Third leg with ischium unarmed; merus 3.9 
times as long as broad, armed on distal inferior 
margin with acute tooth; carpus and propodus 
so rotated that dactylus lies at 90° to plane 
of merus, similar to A. malleodigitus, carpus 
with marked twist immediately beyond meral- 
carpal articulation; carpus about 0.6 as long 
as merus, armed on distal superior and inferior 
margins with acute teeth; propodus slender, 
tapering, slightly shorter than carpus and bear- 
ing five movable spines on inferior margin, two 
distally; dactylus curved and simple. Fourth legs 
similar except meral tooth of lesser develop- 
ment. Fifth legs with well developed brush on 
propodus. 
Telson 4.7 times as long as distal margin is 
broad, 2.5 times as broad anteriorly as poster- 
iorly, lateral margins slightly convex, tip 
shallowly arcuate; medial pair of terminal 
spines almost as long as posterior margin is 
broad; dorsal spinules of moderate develop- 
ment. Telson without anal tubercles. Outer 
uropod with definite articulation. 
DISCUSSION: Unfortunately, the large chela 
is not present on either specimen; however, we 
believe it would be safe to predict that the 
chela will be similar to those of the Obeso- 
manus group or similar to those species previ- 
ously placed in the genus Thunor. The species 
plainly belongs to the Obesomanus group. 
Within the group it is closest to the species 
previously placed in Thunor , which also have 
vestigal scaphocerites, but it may be distin- 
guished from them by the presence of the 
tooth on the merus of the third legs, the form 
of the telson, and the presence of an articula- 
tion on the outer uropods. 
The characteristics of this species demand a 
reconsideration of the separation of Arm- 
strongs genus Thunor from the genus Alpheus, 
In a previous paper (Banner, 1956:365) the 
criteria for the genus Thunor were reviewed, 
and the conclusion was reached that two 
characteristics only would serve to separate the 
two genera: the lack of anal tubercles and the 
lack of an articulation on the outer uropod, 
both found in the genus Thunor . This species 
has the articulation but lacks the anal tubercles; 
therefore, the only criterion remaining is the 
articulation of the uropod. On the other hand, 
the species in the Obesomanus group and in 
Thunor present a somewhat uniform transition 
in other characteristics between a typical 
Alpheus- form as found in other groups, and 
the extreme of Thunor, such as T. micros cap his 
Banner or T. rathhunae (Schmitt). We do not 
believe that this single criterion is sufficient to 
separate Thunor from Alpheus; thus the name 
Thunor should be put into synonymy. Thunor 
could be retained, if desired, as an infrageneric 
group, but here again the group would be 
difficult to define. Therefore we are placing 
the species previously attributed to Thunor 
into the Obesomanus group, including A. 
idiocheles Coutiere, in spite of the fact that 
Coutiere placed it in the Macrochirus group. 
CRINITUS GROUP 
Alpheus frontalis H. Milne-Edwards 
Alpheus frontalis Milne-Edwards, 1837. Hist. 
Nat. Crust. 2:356. 
