u6 Records of the Indian Museum. [Vol. XXIV, 



occur for the most part in sheltered portions of the littoral zone 

 and are especially abundant in the vicinity of coral-reefs. A small 

 proportion occur in moderate depths, up to 50 fathoms, and a 

 few live in deeper water. The greatest depth from which any 

 Pontoniine is known is 703 fathoms. 1 



The most remarkable feature of the subfamily is the ability its 

 members have shown in forming associations with other animals. 

 In the variety of these associations they excel all other Caridea. 

 Some are found on Sponges, others on Actinians, Alcyonaria and 

 Madrepore corals, a few are to be met with on Asteroids and 

 Echinoids and many live on Crinoids. A considerable number of 

 species occur in the mantle-cavity of Lamellibraneh molluscs and 

 some are known from the branchial sac of Ascidians. Many species 

 are, of course, free-living, but the association between a prawn and 

 some other animal can usually be detected only by the collector and 

 unless the facts are carefully noted on the label they are liable 

 to escape notice. I have little doubt that many more species 

 possess these associations than we now realize. 



As to the nature of the association we are at present very 

 ignorant. The species that live in Iyamellibranchs and in Ascidians 

 find a safe retreat from the perils they would meet outside and 

 through the activities of their hosts are, no doubt, well supplied 

 with food. They are commensals in the strict application of the 

 term and, in so far as they deprive their hosts of a portion of their 

 nutriment, may also be regarded as parasites. In the absence of 

 any evidence that their presence is of advantage to the host, they 

 cannot be called symbiotic in the sense in which the word is gener- 

 ally applied. 



The species that live on the giant sea-anemone, Discosoma , 

 are probably protected by their host and those that live on 

 Sponges, Alcyonaria, Madreporaria and EchinOderms doubtless 

 obtain the benefit of shelter. The species on Discosoma perhaps 

 share the food of their host, but it is not unlikely that those on 

 Alcyonaria feed directly on the polyps and are thus true parasites. 



Dr. Asajiro Oka found two remarkable species of Pontonia 

 when examining the Indian Museum collection of Tunicates and 

 has pointed out that the size of the prawns indicates that they 

 must have entered the Ascidian in the larval state and grown up 

 to maturity in the branchial sac. In a specimen of Polycarpa 

 annandalci Oka, in which the external measurements of the test 

 were 33 mm. x 23 mm. X 19 mm., a male and female of Pontonia 

 anachoreta, sp. nov., were found, the prawns being 6 - 5 and io - 5 

 mm. in length. From Ascidia willeyi Oka, with test 35 mm. x 

 20 mm. a pair of Pontonia okai, sp. nov., 8 and 8*5 mm. in length, 

 was obtained. When it is considered that these Pontoniids are 

 heavily built forms, with one of the chelate legs of the second 

 pair extremely large, it is evident that they could not possibly 



1 A specimen of Periclimenes I accadiz'eusis collected by the R.I. M.S. 

 ' Investigator.' 



