L64 CEYLON PEARL OYSTER REPORT. 



congener. The bidentate character of the apex <>t the tylostyle is very remarkable, 

 especially in comparison with the mucronate character of the corresponding spicule in 

 P. serraboha/niata. 



R.N. 2G3a (Gulf of Manaar). 



Iotrochota, Ridley. 

 Esperellinse of massive, ramose, or flabellate form, and usually of dark purple or brown 

 colour. Skeleton reticulate. Megascleres styli, to which diaetinal forms may 

 be added, especially in the more superficial parts of the sponge. Typical micro- 

 scleres birotulate (apparently modified isocheke). 

 In previous papers I have used the term " Amphiaster" for the birotulate spicules 

 of this and certain other genera of Esperellime. There can, however, be little doubt 

 that these microscleres are modified isochelre, and do not belong to the astrose series 

 at all. They are connected with the more typical isochelse by the peculiar isocheke 

 of the genera Choudrocladia and Axoniderma, and may conveniently be termed 

 " birotulate isochelse." 



Iotrochota purpurea (Bowerbank), Ridley. 



1875, Halichondria purpurea, Bowerbank (49) ; 1884, Iotrochota purpurea, RlDLEY (16). 

 The Ceylon variety of this species is characterized by its dark brown instead of 

 purple colour in spirit.* It is also easily distinguished from Iotrochota baculifera by 

 this character as well as by the replacement of the tylote megascleres by slender styli, 

 commonly arranged in radiating tufts at the surface. 



The specimens are for the most part irregularly cylindrical in shape, may be much 

 branched ; and the surface is covered irregularly with small, sharp conuli. The styli 

 of the main skeleton are usually sharp-pointed and very variable in size. The 

 birotulate isocheke are numerous and about 0'02 millim. long. Not infrequently, the 

 straight, slender styli in the radiating tufts at the surface of the sponge exhibit an 

 inflation not far from the middle of the shaft, causing them to resemble a pipette. 

 The fibres of the main skeleton reticulation are stout and contain much spongin as 

 well as very many spicules. 



The original type of the species was described by Bowerbank from the Straits of 

 Malacca. Ridley recorded it from Torres Straits, Albany Island, Port Molle, and 

 the Amirante Group. The West Indian Iotrochota birotulata (Higgin) (53) and the 

 Southern Australian Iotrochota coccinea (Carter)"!" are very possibly identical with 

 this species, or only varietally distinct. 



R.N. 258; 297; 309; 343; 354; 360 (Stat. V., off Chilaw, 10 fathoms, and 

 elsewhere in Ceylon seas. Some are mere fragments). 



* It should, however, be noted, that a portion of the collection was preserved in formalin and trans- 

 ferred to spirit afterwards. I do not know which specimens were treated in this way, nor do I know 

 what effect such treatment may have had upon the colour. t Vide Dendy (10). 



