50 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



It clearly indicates that this fauna is an integral part of that of 

 the Malay region, not a distinct and separate one, and that in the 

 southern part, especially in the Sulu Archipelago, the abundance and 

 variety of ascidians is very great. Proceeding northward among the 

 islands, the ascidians appear to gradually diminish both in abund- 

 ance and variety. The Albatross collection fails to give any indica- 

 tion that this decrease is compensated for by the appearance of 

 northern forms ranging southward from the temperate regions of 

 China and Japan. The very few forms common to these regions and 

 the Philippines are widely distributed species whose presence does 

 not signify any special faunal relationship between places where 

 they happen to occur. The ascidian fauna of the Philippines is 

 distinctly a tropical one. Its relations to that of the temperate por- 

 tions of the Australian coast are in fact much closer than to those of 

 the less distant regions on the north, since on account of the warm 

 currents many tropical Malayan forms range southward along the 

 east coast of Australia to and even through Bass Strait. In arriving 

 at these conclusions the fact must be kept in mind that insufficient 

 collecting has been done in the northern part of the Philippines, and 

 the presence of certain northern forms there may yet be established, 

 but it seems hardly likely that they occur there to such an extent as 

 to render necessary any great modification of the views here ex- 

 pressed. 



REVIEW OF LITERATURE. 



Gould (1852-1856) x figures several ascidians from the Sulu Sea, 

 but accompanies the illustrations with very little description or other 

 information. On plate 52 of Gould's Atlas (1856) the following 

 are shown: 



Figs. 613, 613a. "Ascidian from Balabac Passage, Sooloo Sea." (This is ap- 

 parently a compound species of the family Styelidae different from any col- 

 lected by the Albatross, perhaps a member of the genus Diandrocarpa.) 



Figs. 616, 616a. " Eucoelium erubescens G., of a spongy texture, attached to 

 coral from the Sooloo Sea." 



Figs. 617, 617a. " Eucoelium , from coral reef, Balabac Passage, Sooloo 



Sea." (The figures do not suffice to determine what these were, but it is pos- 

 sible that they are both identical with Polysyncraton dubiam Sluiter of the 

 present paper.) 



Figs. 621, 621a, 621b. " Nephtheis ( ?) , dredged from about 9 fathoms, 



Sooloo Sea." (This is Nephtheis thompsoni (Herdinan) of the present paner.) 



The Challenger Expedition, 1873-1876, collected a number of ascid- 

 ians in Philippine waters which were described as species new to 

 science by Herdman (1881, 1882, 1886) in the reports of that expedi- 

 tion. The list of them follows. The names for these species adopted 



1 See list of literature at the end of this paper. 



