24 



ix. RHIZOTROCHUS, Edw. & H., Martin Duncan. 

 18. Rhizotrochus crateriformis, Alcock. 



Rhizotrochus crateriformis, Alcock, Journ. As. Soo. Bengal, Vol. LXII. pt. 2, 1893, p. 170, pi. viii. figs. 1, 2 : and 

 Vol. LXIII. pt. 2, 1894, p. 187. 



Only four specimens have been dredged, and three of them are impacted 

 in dead coralla of their own species, which has caused great irregularity of 

 growth. The description applies to a clean free specimen dredged off the 

 Coromandel coast at a depth of 573 fms. 



The corallum is low, bowl-shaped, having a small central mamillary scar, a 

 very thin fragile thinly-epithecate wall, and a circular orifice with the lip 

 gently everted. (In the impacted specimens the calicular orifice is, in a 

 general way, broadly-elliptical, but is about as irregular as it can be). 



From the thecal wall, which is marked with close faint longitudinal and 

 transverse strise, a few large cylindrical rootlets stand out at a wide angle. 



The septa are in four complete cycles and an incomplete and inconspicu- 

 ous fifth : at, and for some considerable distance below, the calicular margin 

 they are mere ridges, but comparatively low down in the calicle they jut out 

 strongly, so much so that in the case of the first three cycles they look almost 

 like large pali : they are thin and have sharp edges, and their surfaces are 

 marked with concentric lines of granules or spicules. The septa of the first 

 two cycles are about equal though there is no complete uniformity among 

 them and are not very greatly larger than those of the third cycle though 

 there is considerable irregularity of size in this cycle also. All three cycles 

 meet at the bottom of the calicle to form a sort of trabecular columella : above 

 this they leave a wide clear space. The septa of the fourth cycle are very 

 much narrower than most of those of the third. 



Colour in spirit both of corallum and of soft parts white. 



The type was dredged on a muddy bottom off the Coromandel coast at a 

 depth of 573 fms. Subsequently 3 large specimens were dredged off Madras 

 at the very different depth of 83 fms. 



The principal septa sunken below the calicular margin gives this species a 

 remarkable appearance. 



Family OCULINID.E, Edw. & H., Martin Duncan. 



x. LOPHOHELIA, Edw. & H. 

 19. Lophohelia investigatoris, n. sp. PI. iii. figs. 1, lar-l. 



Corallum in irregularly ramifying colonies, but proceeding by regular 

 alternate distichous subterminal gemmation, occasionally dichotomous. 



