'868.] DR. J. E. GRAY ON THEONELLA. Sgo 



the cysts covering the ends of the mass like the rest of the body. 

 The cysts are hard, cartilaginous, rather convex externally, with two 

 concavities having an opening at the base of each. The apertures 

 are slightly raised round the edge ; and the centre is closed with 

 four short valves, leaving a stellate 4-rayed aperture. The outer 

 surface of the cyst is covered with a thick hard skin, strengthened 

 externally with imbedded particles of sand, which are mor'e abun- 

 dant and clustered in certain parts, especially in those sunk below 

 the general level of the surface. The animal is full of sand, in 

 rhombs and crystals. 



6. Note on TheoneUa, a Ncav Genus of Coralloid Sponges 

 from Formosa. By Dr. J. E. Gray, F.R.S., V.P.Z.S., &c. 



Mr. Swinhoe sent to the British Museum in 1867, alono- with 

 some other marine productions, a small specimen of coralloid spono-e. 

 The outline of the cup is irregular, and the base of the cavity im- 

 perfect, which induced me to consider that the species was imperfectly 

 developed. Though I promised to describe it, I have waited in hopes 

 that I might obtain a more perfect specimen ; but Mr. Swinhoe has 

 now left Formosa, and informs me that he is not likely to obtain 

 any other specimen. The sponge in some external characters is like 

 the genus Macandrewia, ijut it differs from that sponge in not 

 having any stellate spicules, or at least Mr. Cooke, who has kindly 

 examined the sponge for me, did not discover any. It is, I believe, 

 the only sponge of the family in which they have not l)een disco'- 

 vered. 



Theonella. 



Sponge cup-shaped, thick, covered with a smooth rather coria- 

 ceous external coat ; internally formed of netted spicules, arranged 

 so as to leave an hexangular mass ; the spicules subcylindrical, united 

 at the mosculation of the network by a siliceous callosity ; the body 

 of the spicules generally smooth, but sometimes slightly spiculate on 

 the surface, with numerous very slender fusiform spicules of very 

 different sizes mixed in the sarcode. The parietes of the cup are 

 pierced with many cylindrical tubes opening on the edge of the cup ; 

 but there is no appearance of any spines or oscules on the edge or 

 surface of the dry specimen. The spicules form a coral-like net- 

 work, very like Macandrewia. Their intersections are rough and 

 tubercular, like the knots of a net, but more rugose ; the spicules 

 themselves are generally smooth ; but some of them are more or less 

 spinulose, with short acute tubercles. The fusiform spicules in the 

 sarcode are abundant, very slender, slightly tapering and acute at 

 each end ; they vary greatly in length, but are always slender and 

 smooth ; they are generally straight, but some few a're curved like 

 a nearly expanded bow. 



Proc. Zool. Soc— 1868, No. XXXVII. 



