3893.] A. Alcock — Newly -recorded G orals from the Indian Seas. 141 



The very deeply seated columella is large and concave, and consists 

 of numerous close-set, blunt pinnacles. 



In the type specimen the height of the corallum is 11%5 mm., the 

 major diameter of the calice 10 mm. and the minor diameter 8 mm., 

 and the diameter of the pedicle 5 mm. 



The septa, pali and columella are of a dull purple-black colour. 



Dredged off the Arrakan Coast by the " Investigator : " . 



The distinctive characters of this species are (1) the delicacy of 

 the calice wall in comparison with the stoutness of the septa and pali, 

 (2) the large size of the pali and the very distinct definition of the 

 palar zone, and (3) the punched-out appearance of the deep-seated 

 columella. 



Heteroctathus, Edw. & Haime. 



7. Heterocyathus cequicostatus, Edw. & Haime. 



Heterocyathus cequicostatus, Milne-Edwards and Haime, Hist. Nat. 

 des Corall., vol. ii, p. 51. 



Numerous specimens were dredged by Professor Wood-Mason in 

 the Andaman Sea. Every specimen has the base perforated and tun- 

 nelled for the residence of a worm, which no doubt lives as a commensal 

 with the coral zoophyte, as I shall be able to show in the parallel case 

 of Heteropsammia. 



8. Heterocyathus philippensis, Semper. 



Heterocyathus philippensis, Semper, Zeitschr. Wiss. Zool., vol. xxii 

 1872, p. 254, taf, xx. figs 12-14. 



Two specimens were dredged by Professor Wood-Mason in the 

 Andaman Sea. 



9. Heterocyathus ivood-masoni, n. sp. Plate V, figs. 4. 4a. 



The corallum is either low and discoid, or if it is higher it is so 

 faintly and truncately conical that the diameter of the base is not much 

 greater than that of the shallow plane calice. 



The costae, which begin on the flat basal surface near its margin, 

 are equal, regular and very finely granular, and are separated from one 

 another by deep incisions. 



The calice is circular and quite flat, except for a central umbilica- 

 tion which marks the columella. 



The septa are in four cycles, of which those of the third cycle are 

 by far the smallest, while the primary septa along with the nearest 

 quaternary of the adjoining half-system on each side are the largest. 

 The six large primary septa with their large quaternary on each side 

 thus form a six-rayed star, each ray consisting of three equal seg- 

 ments — namely a primary septum with a quaternary on each side of it. 



