XV. NOTES ON CRUSTACEA DECAPODA 

 IN THE INDIAN MUSEUM. 



X . H YMENOSOMA TIDAE. 



By StanIvEy Kkmp, B.A., Superintendent, Zoological Survey 



of India. 



The small crabs belonging to the family Hymenosomatidae 

 are singularly unobtrusive in habit and unless very abundant are 

 liable to escape notice. A few species are found in salt water of 

 no great depth, and are not infrequently taken on coral reefs or 

 living under stones between tide-marks ; but the majority (at an}^ 

 rate on the Indian coast) appear to inhabit estuaries or lagoons 

 where the water is of low or variable salinity. Two species of the 

 family have, indeed, succeeded in establishing themselves in pure 

 fresh water and one has been taken in lakes 3,000 ft. above sea 

 level. ^ 



Most of the species prefer a bottom composed of mud, which, 

 when matted with the fine hairs on their bodies, doubtless assists 

 them in escaping detection. In many instances the mud forms such 

 a dense coating on the carapace and appendages that it is almost 

 impossible to remove it without injury to the specimen. The legs 

 are very brittle ; some species appear to throw them off almost 

 without provocation, and this so constanth'- occurs with Elamena 

 {Trigonoplax) iinguiformis that it is almost impossible to preserve 

 a perfect example. 



Among the crabs recently collected on the Indian coasts 

 several species of Hymenosomatidae are represented. Alcock in 

 his memoir on the Indian Catometopes* was able to give an account 

 of five species and two more have since been recorded. Six others, 

 all of which have not hitherto been described, are here added, 

 bringing the total number of known Indian forms up to thirteen. 



The new Indian species were all obtained in brackish water. 

 Four were found by myself in Portuguese India, one being a very 

 abundant species which has also been collected by Dr. F. H. Gravely 

 in the Cochin backwaters. The other two were taken by Dr. 

 Annandale and myself in the vicinity of Calcutta. Both these 

 species exhibit very peculiar structure and one of them, obtained 

 on the banks of the River Hughli, cannot be included in any of 

 the genera hitherto described. There can be no doubt that numbers 



^ Halicarcimis lacustris (Chilton) [see p. 247, footnote] and Rhvnchoplax 

 introversiis, sp. nov. 



■^ Alcock, Joiiru. Asiat. Soc. Bengal, I, XIX, p. 385 (l90(?). 



