1922.] S.Kemp: Notes on Crustacea Decapoda. 119 



and even when the actual tints are variable the distribution of the 

 pigment is frequently constant. A colour description of Coralliocaris 

 snperba made at Port Blair agrees in a wonderfully exact manner 

 with the coloured figure published by Dana in 1852 ; had there 

 been any doubts as to the identity of the species the evidence of 

 colour would have been most helpful. 



The colouration of man}' species of Pontoniinae is very strik- 

 ing and there can be little doubt that in some cases it is pro- 

 tective. Potts ' has observed that the rather strikingly coloured 

 species which live on Crinoids usually harmonize well with their 

 hosts and a remarkable correspondence with the host in both 

 pigment and pattern was noticed by Col. Alcock 2 in a Pontonhd 

 associated with Pteroeides. 



But protection will not always supply an explanation. Of the 

 two Pontoniids associated with Discosoma, one, P. inomatus, is 

 protectively coloured ; it is semitransparent, without any pigment- 

 ation whatever, and can only be detected with difficulty as it 

 crawls among the short tentacles of the Actinian. The other 

 species, P. brevicarpalis , though very closely allied, is pigmented 

 in a most remarkable manner and is probably one of the most 

 gorgeous prawns in existence. By reason of its colour it is always 

 excessively conspicuous. Periclimenes rex, another species with 

 very brilliant colouration, is perhaps associated with a red and 

 white sponge and it is possible that the colour, though very bright, 

 is protective. 



In addition to the rich collection of the Zoological Survey of 

 India, I have been able, thanks to the courtesy of Prof. Ch. Gra- 

 vier, to examine a number of undetermined specimens belonging to 

 the Paris Museum. Among other interesting species this collec- 

 tion contains a very remarkable prawn for which I have proposed 

 the new genus Thaumastocaris. To Dr. W. T. Caiman I am in- 

 debted for much assistance while working at. the British Museum 

 and to Dr. C. Forster Cooper for the opportunity of examining 

 some of the species described by Borradaile. 



The types of the new species, unless otherwise noted, are in 

 the collection of the Zoological Survey of India. 



Key to the genera of Pontoniinae. 



A. Mandibular palp present, usually composed of two seg- 

 ments [rostrum laterally compressed with conspicuous 

 teeth ; dactylus of last three legs (? always) simple]. 

 B. Second maxilliped with podobranch ; first pleopod 



of male with appendix interna [free-living] ... Urocaridella, p. 



B. Second maxilliped without podobranch ; first pleo- 122. 



pod without appendix interna [frecrrliving or asso- 

 ciated with crinoids] ... ... ... Palaemonella, p. 



A'. Mandibular palp absent. 122. 



B. Antennal scale well developed. 



■ 



' Potts, Public. Carnegie Inst. Washington , no. 212, p. 81 (1915). 

 2 . Alcock, A Naturalist in Indian Seas, p. 14 (1902). The species on which 

 this observation was made is Dasycaris symbiotes, gen. et sp. nov. 



