74 CEYLON PEARL OYSTER REPORT. 



0'04 millim. in longer diameter; they are densely crowded together, and either 

 eurypylous or with very short, wide exhalant canaliculi. 



This species is so peculiar that it might almost form the type of a new genus, but 

 I cannot fix upon characters which would separate it absolutely from SOLLAS'S 

 Myriastra. The sponge, however, is not exactly small, nor are the oscules distinct, 

 nor are the pores in sieves, nor yet is the ectosome thin ; all of which features are 

 mentioned by SOLLAS as characters of Myriastra, though I should hardly consider 

 them as being of generic value myself. 



RN. 128, 128A, 128B, 130 (Station XLL, 12 miles off Galle, 100 fathoms). 



Pilochrota, SOLLAS. 

 Microsclere a euaster of one form only. Ectosome differentiated to form a cortex. 



Pilochrota haeckeli, SOLLAS. Plate II., fig. 4. 

 1888, Pilochrota haeckeli, SOLLAS (15). 



There are eight specimens in the collection which agree so closely with SOLLAS'S 

 description as to leave no doubt of their specific identity with the " Challenger " 

 species, represented in the " Challenger " collection by a single specimen from the 

 Philippine Islands. The Ceylon specimens are irregularly spherical or oval in shape, 

 and the largest is about 16 millims. in maximum diameter. The colour in spirit is 

 grey. The vent (when visible) is. single, small, and surrounded by a membranous lip, 

 minutely hispid owing to projecting oxea. The inhalant pores are arranged in small 

 sieves, which are irregularly scattered or situated in shallow meandering grooves. 

 The sponge has a strong tendency to attach itself to foreign objects by means of short, 

 root-like processes. 



I subjoin the spicular measurements taken from one specimen (li.N. 127), in 

 support of the identification : 



(1.) Orthotrisenes (Plate II., fig. 4, a) ; shaft, 2'3 millims. by 0'074 millim., 

 gradually and sharply pointed; cladi, 0'3 millim. long, stout, conical, sharp-pointed, 

 expanded almost at right angles to the shaft, slightly recurved. 



(2.) Anatrisenes (Plate II., fig. 4, c) ; shaft, 2'8 millims. by 0'037 millim., long 

 and slender, finely pointed ; cladi, strongly recurved, fairly stout, sharp -pointed, 

 0'13 millim. long. 



(3.) Somal oxea; fusiform, gradually arid sharply pointed at each end, symmetrical, 

 often slightly curved ; measuring about 2'3 millims. by 0'04 millim. 



(4.) Cloacal oxea ; small and slender, about 0'2 millim. by 0'005 millim. 



(5.) Chiasters, with very slender, tylote rays; total diameter about 0'012 millim., 

 not very abundant. 



(There are also a few curiously abnormal truenes with very short and stout shafts, 



