The Marine Fauna of the Mergui Archipelago. 155 



and are found either in the " Investigator " or in the " Siboga " lists ; in most 

 cases, indeed, they appear in both lists. With one exception, the others are 

 also previously known forms, but their presence in the Mergui Archipelago 

 extends, in some cases considerably, their geographical distribution. For 

 example, Ophiomastix venosa, while common in the western part of the 

 Indian Ocean, has not hitherto been found east of the Maldive and the 

 Laccadive Islands ; and Lutkenia cataphracta, originally described by Brock 

 (1888) from a single example captured off Cape York, North Australia, has 

 now for the first time been found in the Indian Seas. Further additions to 

 the fauna of the Mergui Archipelago are Ophiactis savigyni, Ophiocoma 

 valenciae, Ophiothrix exigua and Astrophyton clavatum. 



The most interesting Ophiuroid, however, in the collection is undoubtedly 

 a new species of Ophiopteron. One hesitates in establishing a new species from 

 a solitary example, even for a form with such distinct characters as are 

 exhibited by an Ophiopteron, since the study of the Ophiuroidea has passed 

 into the hands of experts, who alone are entitled to say whether a certain 

 specimen is or is not a new species. Accordingly, before publishing this 

 paper, I sent the example to Professor Koehler, who kindly examined it for 

 me. It was with great pleasure that I read Professor Koehler's confirmation 

 of my diagnosis of the specimen as a new species of Ophiopteron, and I most 

 cordially thank him for his courtesy in connection with this and other 

 matters bearing on this communication. I have figured the new species, 

 Ophiopteron gymnatum, and have described it in detail. 



All the examples in the collection are essentially types characteristic of 

 the shallow-water Ophiuroidea of the Indo-Pacific Ocean, and while some of 

 the species are better known from the western side of the Indian Ocean, 

 most of them are rather representative of the seas round the Western 

 Pacific Islands. If one can come to any conclusion as regards the distribution 

 of Ophiuroidea in the Mergui Archipelago from the frequency with which 

 the same species occurs at different stations, then the most widely distributed 

 species in this limited area are Pectinura gorgonia, Ophioglypha sinensis, 

 Ophiothrix stelligera and Ophiothrix hirsuta. It would also appear that 

 Hastings Harbour, Station XXII., where the bottom is rocky and sandjr, 

 and the depth varies from the shore to 20 fathoms, is, of the local areas, 

 most prolific in Ophiuroidea, for eight species were collected there. But 

 this abundance may be accounted for by the fact, that, in addition to 

 shore collecting and the employment of a dredge, a diver was employed 

 in the investigation of the deeper waters. In this connection Dr Eudmose 

 Brown (1910) says : — " We instructed our divers to bring up anything they 

 could find in addition to pearl and mother-of-pearl oysters. This is probably 



