HYDROMEDUSAE, SIPHONOPHORES, AND CTENOPHORES. 349 



Medusae were collected at only 57 of the 571 stations occupied, and 

 few species were taken at more than 3 or 4 stations each. They do 

 not suffice for an attempt to plot their occurrence among the Philip- 

 pine Islands. But when we add to them the records of the recent 

 collections from Malayan waters (Siboga Maas, 1905; Bedot, 1906) 

 and from the west coast of Sumatra (Valdivia Vanhoffen, 1902, 1908 y 

 1911), and Mayer's (1915) list from Torres Straits, we have suffi- 

 cient data for a tentative discussion of the relationship of the Medusa 

 fauna of the Philippine-Malayan region to that of other parts of the 

 Indo-Pacific. 



The most obvious comparison is between the Philippines and the 

 Malay Archipelago sensu stnctu. Out of the total of 26 Philippine 

 species, 15 were taken by the Siboga, by Bedot at Amboina, or by 

 the Valdivia off the west coast of Sumatra. Three are new, and all 

 of those which remain have been recorded either from the tropical 

 Pacific, from the Indian Ocean, or from both. Furthermore, all 

 recorded Malayan forms not collected in the Philippines are re- 

 corded from the Pacific or from the Indian Oceans, or both, except 

 five, which are known from only a single record each, and five known 

 from the Atlantic or represented there by hardly distinguishable 

 allies. 



There would be no reason on geographic grounds to expect any 

 separation between Philippine and Malayan waters, so far as their 

 medusae are concerned, and the data outlined above shows that there 

 is none. Indeed, it is surprising that the apparent unity is as great 

 as it is, when we remember how little work has been done in either 

 region, the difference being no greater than would naturally be ex- 

 pected for any two different collections made several years apart. 

 There is no conclusive evidence that either has any medusae peculiar 

 to it, for a single record can not be given that weight, even if the 

 form in question has never been taken elsewhere. 



In the following pages the surface species and those belonging to 

 the intermediate depths are treated separately, because the two 

 groups are subject to very different environments. 



1. Surface Species. 



Under this term are included all species known from the surface, 

 except for Halicreas papillosum, a typical "intermediate" form 

 which has been taken sporadically at the surface (Bigelow, 1909a). 

 I have also included two species, Pvotiara tropica and Phortis elli- 

 ceana, for which we can not yet assign a definite habitat, but which 

 probably are epiplanktonic. In the accompanying table (p. 350) the 

 records of the Philippine-Malayan surface species is plotted, for 

 various parts of the Indo-Pacific region, from east to west, only 



