76 Papers from the Department of Marine Biology. 
Coutiére goes on to remark that his group is— 
“differentiated from the other groups by some marked characters, which are 
almost all characters found in the Hippolytide and therefore suggest a less 
strong resemblance to the Reptantia; as frequently happens, there are added 
to these primitive characters (others) which show on the contrary, an adapta- 
tion carried very far; for instance, the strongly curved hooks and the movable 
finger of the small chela surpassing the fixed finger; these characters are espe- 
cially marked in S. comatularum and are explained by its commensalism with 
the comatulid, being implements of attachment for the Synalpheus.” 
Both the species which I have collected belong to this group. More- 
over, two other forms which are included by Coutiére are distinctly 
stated in the original descriptions as occurring on crinoids. These are: 
Synalpheus stimpsonii var. maldivensis, and Synalpheus carinatus var. 
binongeensis (from Comatula). 
Thus, 4 out of the 12 species and subspecies in the group possess this 
habit. As, for the most part, the different forms are only known from 
very few specimens, and notes on the habits or even colouration of the 
living animal are hardly ever given, I think it highly likely that exten- 
sion of our knowledge will show that the whole group is characterized 
by commensalism with crinoids and possibly also by the striking 
colouration, so different from that of other alpheids, which are found in 
S. brucet and S. comatularum. 
Synalpheus brucei sp. n. (Plate 1, Fig. 2.) 
A Synalpheus of medium size, commensal on crinoids. Body rather slender, 
colouration variable, with longitudinal bands of red or purple pigment. Ros- 
trum very long, about one-third the length of carapace, reaching to the end 
of second antennular article, 
slender and acute, continued | 
backwards for a short dis- 4 
tance beyond the level of the 
eyes as a low carina. Sup- B 
raorbital spines acute, about C 
one-third the length of the 
rostrum. Antenne (2) very 
long and slender; the basal 
joint hardly so long sed the Fie. 1.—Chelse of Synalpheus. 
spine of the scaphocerite. S. brucei: A, large chela, X 4; B, small chela, X 8. 
Antenne (1) very much S. comatularum: C, small chela, X 8 
shorter than antenng; stylo- i ne ha ee 
cerite only reaches to end of proximal article; proximal article much longer 
than other two; spines of basicerite almost equal, external does not extend 
further forward than supraorbital spine. Incisor process of mandible tends 
to end broadly, with several teeth. Large chela with rather inflated propo- 
dite, carpopodite with prominent spine on outer border. Meropodite with 
two smaller spines.- Small chela with dactylopodite not stretching beyond 
end of thumb, meropodite with prominent spine on outer border. First seg- 
ment of carpus of second pair of feet much longer than the four succeeding 
segments together. Third and fourth feet armed with sharp spine on inferior 
