SPONGES. 75 



as shown in fig. 4, b, d, e, but T think that these must be regarded as monstrous 

 forms of the orthotriaenes and anatriaenes, and not as having any taxonomic value.) 



R.N. 127, 127a, 1276, 127c, 127d (all from deep water off Galle and onwards up 

 the West Coast); 197 (no special locality); 215 (deep water outside the pearl banks, 

 Gulf of Manaar); 225 (Station XLI., 12 miles off Galle, 100 fathoms). 



Pilochrota hornelli, n. sp. Plate II., fig. 5. 



The single specimen is shaped like a somewhat elongated potato, with a fairly 

 smooth but rather uneven and finely granular surface, to which a number of foreign 

 bodies, such as shell-fragments, Foraminifera, &c, are attached. In its present 

 condition it measures about 45 millims. by 33 millims. by 33 millims., but a small 

 piece has been cut off from one end. The texture is somewhat spongy internally, 

 but with a firm, dense outer crust nearly 1 millim. thick in places. The colour is 

 light brown throughout. The inhalant pores are arranged in small groups (pore- 

 sieves) thickly and generally scattered over what was probably the lower half of the 

 sponge : they are also scattered singly on the upper part. There is a single large 

 vent near one end of the upper surface, elongated transversely to the long axis of the 

 sponge and with a narrow, thickened, smooth, fleshy margin. The vent measures 

 about 6 millims. by 2 millims., and is the opening of a short, wide oscular tube formed 

 by the union of a number of large exhalant canals. 



The skeleton in the interior of the sponge is loose and irregular, composed 

 principally of large, scattered oxea, not arranged in definite fibres. Towards the 

 surface the spicules tend to collect together into fibres which end in dense brushes 

 composed almost entirely of ortho- and anatriaenes. These brushes separate the wide 

 subcortical crypts from one another, but their expanded outer ends form a continuous 

 spicular crust at the surface. The cladi of the orthotriaenes are for the most part 

 extended at the surface of the sponge, but do not project beyond it, those of the 

 anatriaenes lie somewhat deeper down in the cortex. There are also a large number 

 of orthotriaenes whose cladi lie beneath the subcortical crypts while their shafts 

 project inwards into the choanosome. 



Spicules. (1.) Orthotriaenes (Plate II., fig. 5, a-d) ; with stout shaft tapering 

 very gradually to a narrow, bluntly rounded or sharp apex, and with short, stout, 

 conical cladi extended almost at right angles to the shaft ; two typical examples from 

 a boiled-out preparation gave the following measurements: (a.) Shaft, 1 "5 millims. 

 by 0-0:32 millim.; cladi, 0'123 millim. by 0-03 millim. (b.) Shaft, T017 millim. by 

 0-04 millim. ; cladi, 0115 millim. by 0"033 millim. In the dermal crust one or two 

 of the cladi not infrequently become bifurcate, but this takes place very irregularly, 

 and a good many monstrous forms occur. 



(2.) Anatrirenes (Plate II., fig. 5, e) ; shaft long and fairly stout, not tapering to 

 hair-like dimensions, though, of course, much narrower at the proximal than at the 

 distal extremity ; bluntly or sharply pointed ; cladi stout, strongly recurved, sharply 



l 2 



