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Show 144 DR. J. ANDERSON ON SACCULINA. [Feb. 7, Dorsal fin low, small, pointed, falcate, and situated near the of the posterior third of the body; pectoral flipper subtriangular, pointed and emarginate posteriorly. Uniform dirty white *. Skull rather flat posteriorly, broad in front ; rostrum short, broad at the base and not much tapered ; dentition ||. Hab. The deep channels of the Irrawaddy river, Burmah, from 300 to 900 miles from the sea. 10. Note on the Occurrence of Sacculina in the Bay of Bengal. By J O H N A N D E R S O N , M.D., F.L.S., F.Z.S., &c, Director of the Imperial Museum, Calcutta, and Professor of Comparative Anatomy, Medical College, Calcutta. [Received February 7, 1871.] Some twelve years ago I directed attention to the not unfrequent occurrence of those remarkable forms of parasitic Crustaceans Sacculina and Peltogaster-f on the common shore-crabs of these islands, Carcinus meenas and Pagurus bernhardus. These peculiar types ot parasitic life have been lately referred by Fritz Miiller to a new group, which he has designated Rhizocephala. Since my residence in the East, I have collected marine Crustacea on a large scale, and have critically examined all the species which would have been likely to yield these most interesting parasites, but have succeeded in finding only one species infested by them, and that to the exclusion of Peltogaster. The Crab (Thalamita crenata) which yielded Sacculina is the common swimming species of the rocky shores of the islands and coast of the Bay of Bengal. I have been fortunate enough to obtain only one specimen of the parasite. There is nothing in its outward appearance by which it can be separated from the species which is so prevalent on Carcinus meenas along our coast-a fact of great interest so far as it relates to the geographical distribution of these forms of life, provided that further investigations into the postovular development of the species verify its identity with the European form. In connexion with this, it is curious to note that while Peltogaster has been found hitherto only along the Danish and eastern and western coasts of the British Isles, Sacculina was first discovered by Cavolini on the shores of the Mediterranean. Further research may reveal the occurrence of the latter in the waters of the Red Sea. The specimen of Thalamita crenata which yielded Sacculina was received from the Andaman Islands, in the Bay of Bengal. * I am indebted to Captain Bowers for our specimen of this Cetacean, and for the description of its colour when recently dead. f Proc. Royal Physical Soc. Edinb. 1854, lviii. pp. 412-415; Ann. & Mag. Nat. Hist. 3rd ser. vol. ix. p. 12 et seq pl. i. |