SPONGES. 155 



reticulation are about 0*2 millim. in diameter, and the fibres from about 0'008 millhn. 

 upwards. 



Spicules. Slender oxea (Plate X., fig. 6), slightly curved and more or less gradually 

 and sharply pointed : size about 0*088 millim. by 0"003 millim., but subject to a good 

 deal of variation, and frequently, if not usually, more slender. 



R.N. 4. 5, 50, 108, 113 (all from Gulf of Manaar). 



Siphonochalina, Schmidt. 



( ihalininse of tubular form. Tubes smooth, both inside and out, usually narrow ; each 

 with a large circular vent at the summit. 



Siphonochalina communis (Carter), var. tenuispiculata, nov. Plate VII., fig. 1. 



This variety (Plate VII., fig. 1) agrees very closely in external form with the 

 specimens of Siphonochalina communis described by Carter (5) and myself (3) from 

 the Gulf of Manaar. Mr. Carter gave no measurements of the spicules in the case 

 of the type of the species, but the specimens in Professor Herdman's collection 

 differ rather strikingly from that collected by Mr. Thurston and described by 

 mvself, in that the spicules are very much more slender and very much more 

 numerous in both primary and secondary fibres and in the fibres of the dermal 

 skeleton. In fact, the spicules, though very abundant in all the fibres and occurring 

 throughout the entire, or almost the entire, thickness of each fibre, are so slender as 

 to be almost vestigial, measuring about - 072 millim. by O'OOl millim. 



In skeletal characters, although the spicules are more slender, this variety agrees 

 much more closely with my Siphonochalina crassifibra from the same locality (3) 

 than with Carter's S. communis; differing from S. crassifibra chiefly in the smaller 

 size of the tubes. Thus it has the external form of S. communis combined with the 

 skeletal characters of S. crassifibra, and I therefore propose to regard all three forms 

 as mere varieties of one and the same species. 



Professor Herdmax informs me that the sponge in life had a violet-pink colour. 



Ridley (16) records the species (under Carter's name Tabvlodigitus communis) 

 from Port Jackson, Australia, and also from Kurrachee. 



R.N. 6, 7, 117 (dry, figured; all from Gulf of Manaar, Stat. II., 8 fathoms). 



Sub-family : DESMACELLIN^E. 

 Haploscleridns with monactinal megascleres. Microscleres various. 



Desmacella, Schmidt. 

 Desmacellinre with reticulate skeleton composed of styli or tylostyli. Microscleres 

 sigmata, toxa and trichodragmata variously combined. 



Desmacella tubulata, n. sp. Plate IX., fig. 4. 

 Sponge consisting of cylindrical, tubular processes, more or less widely open above 



x 2 



