134 Records of the Indian Museum. [Vol. XXIV, 



Dana gives the length of the adult female as 8 lines, while a 

 male examined by de Man was 13 mm. in length ; the Indian speci- 

 men is thus much smaller than any previously referred to the 

 species. 



C 353/i- Port Blair, Andamans. S. Kemp, March, 1915. One. 



The specimen was obtained at low water on the reef at the 

 northern end of Ross Island and was not associated with a crinoid. 



Dana described P. orientalis from the Sooloo Sea. The speci- 

 mens described by de Man were obtained on a crinoid at Amboina. 



Genus Periclimenes Costa. 



1831. Pelias, Roux, Mem. sur les Salicoqnes, p. 25 [tiom. praeocc). 



1846. Periclimenes, Costa, Cat. Crost. Napoli (unpaged). 



1852. Anchistia, Dana, U. S. Explor. Exped., Crust. I, p. 577. 



i860. Urocaris, Stimpson, Proc. Acad. Sci. Philadelphia, p. 39. 



1861. Dennisia, Norman, Ann. Mag. Nat. Hist, (3), VIII, p. 278. 



1902. Ancylocaris, Schenkel, Verliandl. naturf. Ges. Basel XIII, p. 563. 



1915. Periclimenaeus and Periclimenes with subgenera Corniger, 



Cristiger and Falciger, Borradaile,- Ann. Mag. Nat. Hist. (8) 

 XV, p. 207. 



1916. Periclimenes subgenus Hamiger, Borradaile, Brit. Antarct. 



Exped. 1 910, Zool. Ill, p. 87. 



1917. Urocaris, Ancyclocaris, Periclimenes and subgenera, Pericli- 



menaeus, Borradaile, Trans. Linn. Soc. (2) Zool. XVII, pp. 333 

 et secj. 

 1919. Periclimenes, subgenera Laomenes and Cuapetes, Clark, Proc. 

 Biol. Soc. Washington, XXXII, p. 199. 



In working through the collection of Pontoniinae in the Indian 

 Museum I have reached conclusions regarding the limits of this 

 genus which, as the above references show, differ widely from those 

 expressed by Borradaile in his recent memoir. That Anchistia 

 and Dennisia are synonymous with Periclimenes has long been 

 well established, but the inclusion of other names in the same 

 category requires explanation. 



Almost at the beginning of my work 1 found the greatest 

 difficulty in distinguishing the three genera Urocaris, Ancylocaris 

 and Periclimenes , and it is evident from the literature that others 

 have found themselves in the same position. In Borradaile's key 

 (loc. cit., 1917, p. 346) the three are placed under primary headings, 

 distinguished for the most part by habit of body. Thus in 

 Urocaris : " Body very slender and compressed. Sixth abdominal 

 segment much elongate"; in Ancylocaris: "Body moderately 

 stout, not compressed. Sixth abdominal segment short " ; in Peri- 

 climenes : " Body never very slender, or much compressed. Sixth 

 abdominal segment never much elongate." The large assemblage 

 of species which these three genera comprise exhibits a very great 

 range of variation in the form of the body and between the most 

 slender and the stoutest ever}' degree of transition can be found. 

 On these grounds it is quite impossible to distinguish separate gen- 

 era with any certainty. Borradaile himself is inconsistent, for in 

 P. parasiticus, which he retains in the genus Periclimenes, the 

 habit of body is extremely slender and the sixth abdominal somite 



