304 CEYLON PEARL OYSTER REPORT. 



attachment consists of a flattened portion spreading over the surface of the coral. 

 The stem measures 2 millims. at the base, and at a height of 17 millims. the 

 first branch is given off. The branching is confined to one plane, the primary branches 

 being given off almost at a right angle. They in turn give off secondary branches or 

 twigs at an angle which approximates even more closely to a right angle. 



The verrucse are placed on the lateral edges of the stem and branches, and are 

 arranged more or less alternately. They are conical and abruptly truncated, with 

 usually a few of the spicules projecting at the opening. The spicules in the calyces 

 are much smaller than those of the general coenenchyma. 



The colour of the whole colony is a beautiful violet tint, with the tentacles of the 

 polyps yellowish in colour. 



The spicules of the coenenchyma are spindle-shaped, either straight or curved and 

 sometimes broad and flat in comparison to their length, or bluntly rounded at the two 

 ends. They can be divided into two fairly distinct types : 



(1.) The larger spicules with rough warts, which vary from 07 millim. to 27 millims. 

 in length and from 0'075 millim. to 0'32 millim. in width ; and 



(2.) The smaller spicules with warts more pointed than rough, which vary in length 

 from O'll millim. to 0'55 millim., and in width from 0'03 millim. to 0'05 millim. 



Another very beautiful form with large violet and colourless spicules seems at first 

 sight very different from the foregoing species and variety. This is mainly due, 

 however, to the fact that there is a prominent opercular covering of small but very 

 conspicuous rose-red spicules sometimes disposed in eight rays. 



Localities : West of Periya Paar, Gulf of Manaar ; deep water off Galle and 

 onwards up West Coast of Ceylon. 



FAMILY: PLEXAURID^E. 



Plexaura praelonga, var. typica (RIDLEY). 



Plexauroides praelonga (WRIGHT and STUDER). 



This species is represented by one specimen, which reaches a height of 425 millims. 

 The branching is confined to one plane and forms an irregular dichotomy. The main 

 stem is 4 millims. in diameter at its base, tapering to 3 millims. at its termination, 

 thus agreeing with the measurements given by WRIGHT and STUDEK. 



The verrucse are numerous and irregularly scattered and the polyps are completely 

 retractile. The coenenchyma is comparatively thin and very friable. The spicular 

 measurements are the same as those given by WRIGHT and STUDER. The colour is a 

 deep brownish-mi in spirits. 



Locality : Outside pearl banks, Gulf of Mauaar. 



Previously recorded from Port Curtis, 5 fathoms to 11 fathoms; Port Denison, 

 4 fathoms; and Station 186, Cape York, 8 fathoms. (See WRIGHT and STUDER 

 (1889), '"Challenger" Reports,' vol. xxxi. : EIDLEY (1884), '"Alert" Expedition,' 

 p. 339, Plate xxxvi., fig. F, and Plate xxxviii., fig. y, g'.) 



