REPORT UPON THE TUNICATA IN THE COLLECTION 
OF THE INDIAN MUSEUM. 
By ASAJIRO OKA, Ph.D., Tokyo. 
(Plates I—V.) 
The collection of Tunicata may, for the sake of convenience, be divided into three 
groups: (I) simple Ascidians, (2) compound Ascidians, and (3) pelagic Tunicata 
including the Ascidiae Salpaeformes, the Thaliacea, and the Larvacea. The present 
report contains a detailed account of the first and third groups; the compound Asci- 
dians, of which there are only a few specimens, will be worked up along with those 
from other sources and will be described and figured afterwards in a separate 
- paper. 
The collection generally was in a fairly good state of preservation, but some of 
the specimens, especially the pelagic forms, were rather in a poor condition, making 
in a few cases the identification extremely difficult. Among the simple Ascidians 
I found two specimens of which the test alone was preserved, so that it was impos- 
sible to determine with certainty to what form they belonged. 
The group of simple Ascidians consists of seventeen species arranged in nine 
genera. Ten of the species seem to be new to science, and for one of these it was 
found necessary to form a new genus. The other group—the pelagic Tunicata— 
contains only one species of Pyrosoma aud five species of Salpa, all of which are well 
known cosmopolitan forms, and a specimen of a very large Appendicularian, appar- 
ently belonging to the genus Megalocercus. The number of species recorded in this 
paper is, accordingly, twenty-four in all. 
This collection, though a small one, is especially interesting on account of its 
containing five well-preserved specimens of an extremely aberrant simple Ascidian, 
very probably belonging to the genus Hexacrobylus, Sluiter. As is well known, this 
genus was formed by Sluiter for a curious deep-sea Ascidian dredged during the 
Siboga Expedition, which in external appearance was so unlike ordinary Ascidians 
that neither Weber nor Sluiter was able to guess its true nature until they cut open 
the only specimen. The description published in the Reports of the Siboga Expedi- 
tion, based upon the examination of the unique specimen, could naturally not be 
quite satisfactory, and yet it has remained the only record of the genus. Under 
such circumstances the five specimens contained in the collection, though represent- 
ing a different species, were extraordinarily valuable, and I paid special attention 
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