Fauna Associated with Crinoids of Tropical Coral Reef, etc. 77 
margin of meropodite; dactylopodite with distinct ventral spike measuring 
about one-quarter the length of joint. Telson with anterior pair of spinules, 
rather slender, situated just behind halfway line; median lobe oval. 
Locality: Murray Islands, Torres Straits. 
Measurements: In seven females measured from the tip of the rostrum to 
the end of the telson the length varied from 1.9 to 2.8cm. The eggs measured 
1 mm. in length; with the growth of the embryo the envelope stretches and 
the egg becomes twice as long. They are always light green in colour. 
Fic. 2.—Synalpheus brucei: A. Lateral 
view of head showing antennz and 
rostrum. b.c., basicerite; b.7., basal 
joint; ex, exopodite (scaphocerite) ; 
8.p., spine of antenna 2; a. 1, 
antenna 1; r, rostrum; s.0., supra- 
orbital spine. X15. 
B. Basal portion of antennal. st., 
stylocerite; 1, 2, 3, articles of pro- 
topodite. X15. 
C. Incisor process of mandibles in 
two individuals, one showing also 
palp (p). X 15. 
S. comatularum: D. Mandible. Inset 
(D’) incisor process of another 
individual. X15. 
Fic. 3.—Synalpheus brucei: A, second 
pair of thoracic feet; B, third pair 
of feet, X 15; C, telson, X 15. 
In these text-figures the correspond- 
ing structures of both S. brucei and S. 
comatularum are given for comparison 
in a few cases, as, for instance, the 
incisor process of the mandible, which, 
though variable in the number of teeth 
in both species (for this reason two 
examples of each are drawn to show 
the range) has a larger number in S. 
brucet. 
RELATIONS OF COMMENSAL AND HOST. 
Comanthus annulatum, with which Synalpheus brucei is usually asso- 
ciated, is very variable in colour. Some indication of this diversity is 
to be found in Dr. H. L. Clark’s account of the Comatulids of Torres 
Straits. Itwill be sufficient here to say that the colouration varies from 
a light green mingled with yellow and white to the darkest green or 
even black. The commensal alpheid is generally black to brownish 
purple in ground-colour, but the pigmented dorsum is traversed by 
longitudinal stripes which are free from pigment. Of these one runs 
down the middle line from head to tail, there are either two or three on 
