EEPOET ON THE MONAXOISTIDA. 211 



much closer resemblance to one obtained by the " Porcupine," and now in the British 

 Museum, than to the original type. 



Locality.— Station 49, May 20, 1873 ; lat. 43° 3' N., long. 63' 39' W.; south of 

 Halifax, Nova Scotia ; depth, 83 fathoms ; bottom, gravel, stones ; bottom temperature, 

 35°'0. One s]3ecimen. 



Habitat. — British Seas (Bowerbank) ; off Shetland Islands (" Porcupine ") ; south of 

 Nova Scotia (Challengei"). 



From the same station (Station 49) there is a second specimen of Polymastia; it is 

 small and attached to a stone. It has three small fistulse and is chiefly remarkable from the 

 presence of a vast number of very long, projecting spicules, which form a deep, velvet-like 

 coat over the body of the sponge. Unfortunately it has been dried up and we cannot be 

 certain of the species to which it belongs ; possibly it is Polymastia mammillaris,^ but 

 probably only a young form. 



Polymastia corticata, Ridley and Dendy (PI. XLII. figs. 4, 5, 5a, 5h, be ; PI. XLIV. 

 fig. 3). 



1886. Polymastia corticata, Eidleyand Dendy, Ann. and Mag. Nat. Hist., ser. 5, vol. xviii. \i. 487. 



Sponge (PL XLIV. fig. 3) massive, sessile, cushion-shaped; with strongly convex 

 upper surface, bearing very numerous mammiform processes ; corticate ; consisting of a 

 dense, leathery cortex about 2'5 mm. thick, and an internal, rather friable, dense, 

 amorphous mass of a pale yellow colour, from which the cortex easily separates. The 

 single specimen in the collection is oval in shape, measuring about 87 mm. in length 

 by 62 mm. in width and 37 mm. in thickness. The mammiform processes are of two 

 very difi'erent sizes — (1) small, very abundant (there are considerably over one hundred 

 on the single specimen), hollow, elongated, generally flattened and closed at the ends, 

 which are frequently pointed ; height about 8 mm., breadth at base 3 mm. (2) Very 

 large, flattened and gradually conical tubes, very few in number (only four or five 

 on the specimen), sometimes open fairly widely at the summit, with a fringe of 

 spicules around the opening, sometimes, however, with no trace of an opening ; height 

 about 25 mm., breadth at base a little over 12 mm. In the immediate neighbourhood 

 of the larger processes the smaller ones are scarce or absent. The larger processes, open 

 at the ends, are evidently oscular tubes, each with a single osculum at the summit, while 

 the nature of the small processes is doubtful. The colour of the sponge in spirit is milk- 

 white (this applies to the cortex only, the internal tissues being pale yellow). The 

 surface is smooth but extremely minutely hispid. Pores in scattered groups of two or 

 three, each group over a small round or oval subdermal cavity ; they seem to occur on 

 every part of the sponge, on both kinds of mammiform processes as well as on the general 

 surface. 



' Vide Bowerbank, Men. Brit. Sjjong., vol. ii. \>. 71. 



