170 A. Alcock — Account of the Deep Sea Collection. [No. 4, 



loose. The oral sphincter is stout. The tentacles of the inner crown 

 are short and number about fifty : those of the outer crown are very- 

 long with stout base and long wavy filamentous ending, and number 

 about sixty. The septa with their mesenteric filaments are almost 

 entirely confined to the upper third of the enteric cavity, leaving about 

 the lower two-thirds as a perfectly smooth-walled chamber. 



Colour dull madder, the tentacles being lighter and ruddier than 

 the body. 



Length, contracted in spirit, 50 mm. 



With the exception of a species from the Andaman Reefs, described 

 in J. A. S. B., Vol. LXIL, Pt. II., 1893, p. 153, this seems to be the only 

 Cerianthns hitherto recorded from India. 



From the Bay of Bengal on a muddy bottom at 410 fathoms : bottom- 

 temperature 45.5° Fahr. 



MADREPORABIA APOROSA. 



Family Turbinolidae. 



(1) Flabellum lacimatum, Phil., and (2) Flabellum japonicum, 

 Moseley, appear to be quite common inhabitants of the muddy bottom 

 of the Bay of Bengal at 400-700 fathoms. And among the corals 

 obtained with them during the past year is a new species of Rhizotrochus. 



Rhizotrochus, Edw. and Haime. 



3. Rhizotrochus crateriformis, n. sp., PI. VIII. figs. 1 and 2. 



Corallum low, bowl-shaped, having a small central mamillary pedi- 

 cular scar, a very thin fragile epithecate wall, and a regular, circular 

 calicular orifice with the lip gently everted. 



From the thecal wall, which is marked with close faint costal stria? 

 and w r ith close faint concentric lines of growth, the large cylindrical 

 " rootlets " stand out at a wide angle. 



The septa, which are in four complete cycles, with an incomplete 

 fifth, are thin, and have their crests strongly emarginate, so that when 

 the corallum is viewed from above they look something like large pali : 

 their surface is marked with lines of distant, coarse granules, concentric 

 with the curve of the crest. The septa of the first two cycles are ap- 

 proximately co-equal, and all unite at the very bottom of the calice by 

 a few stout cylindrical trabecule which form a rudimentary columella : 

 above this they do not encroach very greatly on the calicular space, 

 but leave a clear wide central fossa. The septa of the third cycle are 

 narrow lamina?, those of the fourth are still narrower, and those of the 

 incomplete fifth are merely fine ridges in the upper part of the calicle. 



Colour in spirit — both corallum and soft parts — quite white. 



