82 Papers from the Department of Marine Biology. 



nate with dark green or black. There also occurs another variety, in 

 which the green pigment is replaced by yellow and the darker pigment 

 by red or brown. In the specimen figured (pi. 1, fig. 3), which is 

 typical of the species, there were three yellow stripes alternating with 

 two brown of equal breadth. The chela was yellow with a brown line. 

 In this case, however, the commensal, living on a crinoid in which 

 green predominated, was very conspicuous, and I suppose it to have 

 developed its pigment in association with another crinoid of different 

 colour type. 



Periclimenes pottsi Borradaile. 



This shrimp is comparatively common on the crinoids from the 

 Murray Island reef, but only one or two specimens were obtained at 

 Mabuiag. It is a very transparent creature, and though the general 

 colouration, a beautiful purple, harmonises with the host, there is no 

 distinct arrangement in longitudinal stripes. The low power of the 

 microscopes shows that there is a blue pigment contained in very num- 

 erous small cells which are regularly disposed over the body. Also 

 evenly distributed, but much fewer in number, are cells containing red 

 pigment. These may be spherical or branching. The gut is coloured 

 red. The general effect is thus purple. 



Periclimenes commensalis Borradaile. 



I did not, amongst the living specimens, distinguish this species from 

 P. pottsi, so probably what has been said about the latter species also 

 applies to the former. It may be noticed that these are not the only 

 species of the genus Periclimenes to be found in association with crin- 

 oids. Others are P. cornutus, ceratophthalmus, and brocketti, all found 

 on crinoids from the Maldives, as noted by Professor J. Stanley Gardiner. 



Information about the surroundings of the animals so seldom accom- 

 panies general collections that I fully expect a similar connection to 

 exist in the case of many other species of this enormous genus. 



DECAPODA ANOMURA. 

 GALATHEID^E. 



There are at least three species of galatheids commensal with crinoids 

 in Torres Straits. These are: Galathea longirostris ( = G. elegans), 

 G. inflata sp. n., G. minuta sp. n. These are all small forms from 6 to 

 15 mm. in carapace length and are dark coloured with longitudinal, 

 pigment-free bands, a colour scheme corresponding almost exactly 

 to that of the alpheids. They are not by any means found so com- 

 monly as is Synalpheus, though G. longirostris is not infrequent. My 

 observations do not lead me to suppose that the galatheids occur in 

 pairs on each host, but the absence of evidence on this point may be 

 due to the fact that they are inclined to leave the host whenever dis- 

 turbed. There is no special modification for clinging to the crinoid 



