TETRAXONIDA. 31 



Skeleton typically formed of a network of spiculo-fibre, the primary lines of which 

 proceed upwards and outwards from the inner surface of oscular tubes to the outer 

 surface of the sponge, where their ends form the verrucae ; the secondary fibres join 

 the primary at right angles forming rectangular meshes about 1'25 mm. square. The 

 thickness of the primary fibres is about '7 mm., that of the secondary about '5 mm. 



The ectosomal skeleton consists of fan-like bundles and wisps of spicules, isolated 

 or proceeding upwards and spreading out from the terminal main fibres. 



Spicules. Megascleres. Smooth styles, 590 x 25 yu, curved, with a mucro at 

 the head end. 



Ectosomal spicules, 344 x 12"5 m, sub-amphitylote, fusiform, with a marginal 

 ring of vertical spines at both ends and a terminal central spike at one extremity. 



Microsderes. Palmate anisochelae of two sizes, a large kind 35 ij. long and 107 m 

 broad, with thick shaft ; with triangular palmate tooth, 17'5 /^ long, at the large end, 

 not quite as long nor as broad as the alae ; lower margin of alae convex. Lower 

 central tooth with a curved upper edge produced into a spine. 



A small kind 17'5 /u long, 6"2 m broad ; upper palmate tooth triangular, rounded 

 above, as broad and as long as the alae ; lower border of alae concave ; lower tooth 

 with simple rounded upper edge. 



Bipocilla varying in lengtli from 5 '5 to 11 m, according to the convexity of the 

 shaft which is usually deeply curved ; both ends spathulate, nearly similar, and with 

 crenulate edges, or with 5-7 teeth. 



The fine specimen (No. 184) which constitutes the type of the new species, is 

 24 cm. wide and 25 "6 cm. high. Unfortunately, owing to the very soft nature of the 

 tissues, the sponge has been broken into many fragments. A short stem expands 

 into a palmate portion, from the edge of which arise several compressed digitate 

 branches, usually with round sj^hinctrate oscules along one edge ; the oscules lead into 

 a pseudogastral cavity extending nearly to the opposite edge of the branch. The 

 bipocilla of the new species somewhat resemble those of /. spatulatus, but the difierence 

 in the body form, skeletal arrangement and spiculation are too many to necessitate 

 detailed enumeration. 



A second specimen (No. 202) has two compressed branches rising from a flattened 

 contracted base, the under surface of which is coated with pebbles. The oscules face 

 each other along the edges of the entering angle. The branches are each about 10 cm. 

 in length, the greatest breadth being 4 '5 cm. 



A third specimen (No. 287) of this species, which might, indeed, be regarded as 

 a variety, forms a discoid crust on a small Ophiurid. There are embryos, 340 m in 

 diameter, present, and some, but not all, of these have a plug of peculiar tylote 

 spicules in them, with a ring of anisocheles round the outer end of the bundle. 

 The tylote spicules of the embryo, 161 x 7 '8 /u, have a smooth rounded end 

 surrounded l)y spines, the other end being cylindrical with marginal spines, and a 

 single central spine. 



VOL. IV. 2 E 



