160 CEYLON PEARL OYSTER REPORT. 



anastomosing with one another. The fibres are not very sharply defined and 

 numerous megascleres occur scattered between them. The dermal skeleton is a very 

 well -developed, triangular-meshed, stellate reticulation of stout, multispicular fibre 

 (about 0'05 millim. in diameter). 



Spicules. (1.) Styli ; fairly stout, often slightly crooked, with fairly well-developed 

 oval heads and slightly constricted necks ; sharply and rather abruptly pointed at the 

 apex ; size about - 3 millim. by 0'009 millim. 



(2.) Broad palmate anisochelse, very similar to those of Esperella simonis;* about 

 0'048 millim. long; frequently in rosettes. 



(3.) Minute palmate isocheke ; numerous, about 0'012 millim. long. 



(4.) Large, stout sigmata, C-shaped and contort, with abruptly recurved and very 

 sharply pointed ends ; size about - 08 millim. from bend to bend by 0"006 millim. 

 thick in the middle. 



(5.) Slender toxa with gently rounded curves; up to about 0*08 millim. long by 

 0'002 millim. thick in the middle : often in sheaves (toxodragmata) when young. 



I have been able to satisfy myself by personal examination of Mr. Carter's type 

 preparation of his Esperia plumosa (now in my possession) of the specific identity of 

 the Ceylon form with the sponge recorded bv Carter from Mauritius, and subse- 

 quently from the Mergui Archipelago also. As Mr. Carter's descriptions are very 

 scanty, I have thought it desirable to give the above details concerning what is 

 evidently a widely distributed and characteristic species in the Indian Ocean, 

 distinguished by an exceptionally varied and beautiful spiculation. 



II. N. 298, 328, 361 (three fragments amongst a large number; all from Ceylon 

 seas). 



Esperella crassissima, n. sp. -Plate XL, fig. 6. 



The single specimen is rounded, cushion-shaped, attached by the base to a mass of 

 calcareous debris. The upper surface is strongly convex and bears a single large 

 prominent vent about 3 millims. in diameter. Surface with a more or less strongly 

 marked reticulate appearance, due to the coarse sub- dermal network of very stout 

 spicular fibre, the oval meshes of which are normally covered over by a thin pore- 

 bearing membrane, now mostly rubbed off. Pores scattered in the meshes of the 

 dermal skeleton. Texture (in spirit) rather hard but slightly compressible and 

 resilient ; coarsely fibrous. Colour pale grey. Maximum diameter of specimen about 

 24 millims. 



The main skeleton is a very well-developed reticulation of very stout, compact 

 spicular fibre up to about - 33 millim. in diameter, composed of very numerous closely 

 packed spicules and without visible spongin. The meshes of this reticulation vary 

 greatly in size and shape; perhaps 1*3 millims. would be a fair average diameter. 

 Immediately beneath the surface the main skeleton passes into the more compact 



* Vide (1), Plate XV., fig. 16. 



