104 



20. Sabinotrochus bipatella n. sp. 



Corallum discoidal, with a scar of attachment; granular costae are 

 present, but are distinct only in the peripheral half of the disk. 



Septa in six systems and three cycles, with traces of a fourth. 

 Those of the first cycle are the largest and stoutest. Those of 

 the first two cycles unite to forrn a thin underniined disk-like 

 columella, which half fills the shallow calicular fossa. Those of 

 the third cycle do not unite with those of the second, though 

 they tend to curve towards them ; they do not usually reach 

 the columella. 



Height of corallum about 2 millim. 

 Diameter of disk » 8 » 



21. Discotrochus dentatus n. sp. 



Nearly related to D. investigatoris mihi (Journ. Asiatic Soc. 

 Bengal, LXII, pt. 2, 1893, p. 142, PI. V, Fig. 5,5a) froin which 

 it differs in having the septa less crowded though more numerous. 



Corallum quite flat and discoidal, of thick coarse texture. On 

 the horizontal base is a faint scar of attachment from which 

 numerous equal well-cut costae radiate. 



Septa hardly exsert beyond the thick peripheral margin, in six 

 systems and five cycles, the fifth cycle being incomplete in a few 

 of the half-systems. The septa of the fifth cycle are thin, but 

 those of all the other cyles are coarse and have their edges deeply 

 and coarsely serrated throughout. Thongh the septa of the first 

 cycle are distinctly the largest, those of the second and even of 

 the third cycle are not very much smaller. There is no union of 

 septa, except at the columella, where those of the first three 

 cycles, and usually of the fourth cycle also, meet. 



The columella, which is small and fascicular and consists of 

 little but the united ends of the septa, is studded with a few 

 coarse subprismatic granules. 



The diameter of the disk of the largest specimen is 19 millim. 



