390 Records of the Indian Museum. [Vol. XII, 



refers to the same form as a species of Bithynis, has given the 

 following account of its habits. — " Un Palemonide du genre Bithv- 

 nis Dana merite une mention speciale par son habitat et sa colora- 

 tion. II est absolument transparent, mais se signale par quelques 

 anneaux d'un violet pale sur les appendices et 1' abdomen, et sur- 

 tout par des taches d'un blanc nacre eclatant, occupant la region 

 stomacale tout entiere, le coude de 1' abdomen, I'extremite des 

 rames caudales et les epimeres du deuxieme segment. Ce magni- 

 fique Crustace se tient obstinement dans la zone de protection que 

 circonscrit une grande Actinic assez commune dans les flaques 

 profondes qui separent les Madrepores. Btale sur le sable, le disque 

 oral de 1' Actinic de couleur blanchatre, arme d'un tres grand 

 nombre de courts tentacules urticants, atteint souvent o m. 30 de 

 diametre. Bithynis se tient dans ce cercle, nageant a peu de dis- 

 tance au-dessus, souvent par couples, et se laisse assez aisement 

 capturer a I'aide d'uiie eprouvette pleine d'eau que Ton descend 

 doucement sur ranimal." 



The anemone at Port Blair was one with greenish tentacles, 

 not whitish as in Coutiere's description. It was not uncommon 

 at low water on the foreshore at " Aberdeen" and was sometimes 

 left high and dry by the tide. On anemones from which the water 

 had completely retreated we failed to find any shrimps, even 

 though the whole specimen was dug up and most carefully ex- 

 amined. On the other hand the shrimps were seldom absent from 

 anemones living in a few inches of water, and were easily caught 

 in a tube full of water as described by Coutiere. The A ncylocaris ' 

 was found swimming and crawling on the column of the anemone 

 beneath the fringe of tentacles and wandering occasionally on to 

 the disc. Thor discosomatis had similar habits, but seemed to 

 wander further afield and rarely ventured among the tentacles. 



The curious feature of the shrimps is that in both species the 

 pigmentation takes the form of very large spots almost pure white 

 in colour. This, too, is a characteristic of certain fish, Amphiprion 

 percula (Lacep.) and Tetradrachmum trimaculatum (Riipp.),"^ which 

 also appear to live commensally with the Discosonia ; the latter was 

 found beneath the fringe of tentacles and was black with a broad 

 transverse band of white at the back of the head, extending down- 

 wards to the eye, and a large white spot below the dorsal fin ; the 

 former, which was commonly found swimming among the ten- 

 tacles, was bright orange with three broad bands of white tinged 

 with green and narrowly margined with black. The presence of 

 white patches in all four commensal species is a most curious 



' Coutiere, in this brief description, has scarcelv done justice to the marvel- 

 lous colouration oi Aiicylocai'is aberrans \ the large white patches are frequent 1}- 

 circumscribed by red or orange pigment and on the tail-fan are eye-spots with 

 reddish centres. A complete account of the colouration of this Palaemonid would 

 be out of place in the present paper, but it may be mentioned that the pigmenta- 

 tion varies somewhat in the two sexes and alters considerably with age. The 

 colouration of Thor (fiscosoiiiafis, on the other hand, is apparimtls' constant 

 throughout life. 



^ 1 .im indebted to Dr. B. I., (haudhuii lor llicse deterniin.-ition--. 



