Fauna Associated with Crinoids of Tropical Coral Reef, etc. 



11 



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 2.8 cm. 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. 



FIG. 2. Synalpheus brucei: A. Lateral 

 view of head showing antennae and 

 rostrum, b.c., basicerite; b.j., basal 

 joint; ex, exopodite (scaphocerite) ; 

 s.p., spine of antenna 2; a. 1, 

 antenna 1; r, rostrum; s.o., supra- 

 orbital spine. X 15. 



B. Basal portion of antenna 1. st., 

 stylocerite; 1,2, 8, articles of pro- 

 topodite. X 15. 



C. Incisor process of mandibles in 

 two individuals, one showing also 

 palp (p). X15. 



S. comatularum: D. Mandible. Inset 

 (/)') incisor process of another 

 individual. X 15. 



FIG. 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. 

 brucei. 



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. It will 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 



