136 MR. 0. \V. ANDREWS AND OTHERS ON THE [Feb. 20, 



The skeleton is composed of main lines of multispicular fibre 

 radiating from base to surface, with an irregular reticulum between 

 formed by bundles of one or a few spicules given off from the 

 main lines ; the axial columns alone are present in the tufts. 



The styles, which measure 525 x 12 /j., are curved near the basal 

 end. 



The nearly related species Stylotella polymastia L8ndenfeld, 

 referred to by Topsent I. c. p. 466, is synonymous with Hymenia- 

 cidon fenestratum (Ridley). 



The proper position for the above species appears to be in the 

 Axiuellidse. The skeleton is composed of axial lines of monactinal 

 spicules, the reticulation beiug of secondary importance and absent 

 from the tufts ; some of the spicules show a double curve, 

 characteristic of certain typical Axinellid sponges. 



Distribution. Amboina ; Java ; Christmas Island. 



Microciona dubia, sp. n. (Plate XII. figs. 3, 3« ; Plate XIII. 

 figs. 2 «-/.) 



Sponge forming an almost free or loosely incrusting lamina 

 with margins curled up, with foreign particles adherent to the 

 under surface where the latter is free. 



Colour yellow ; upper surface smooth. Skeleton formed partly 

 of columns, each composed of one stout subtylote spicule, and 

 partly of plumose columns of more slender tylotes opening out 

 from base to surface, where they almost form a distinct dermal 

 layer ; numerous short spined styli arranged vertically with bases 

 on the basal layer of the sponge. Spongin absent. 



Spicules. Megascleres — stout, slightly curved subtylotes 324 x 

 7'5^i, head 7*7 /i, slightly spined, occasionally facetted. 



Slender straight tylotes 318-328^ x 5*5 fx, head 7 /z with basal 

 end spinous. 



Short spined styli 48 x 7*5 /i, with sharp, often curved, spines 

 on the basal three-fourths of the length of the spicule. 



Microscleres — palmate isochelae from 3 to 12 p. Toxa large, 

 slender, 39 x 1 /x ; a shorter but thicker form (numerous), 6 x 1*5 <*. 



The size of the specimen is 2-5 c.c. x 5 c.c. in area, and 1 mm. 

 in thickness. The unispiculate columns, which occur in parts of 

 the sponge, recall the chief character of Ryrnerrhaphia. Again, 

 the spiculation closely resembles that of certaiu species of Rhaphi- 

 dophlus (R. filifer Ridley & Dendy and R. spiculosus Dendy), 

 but the absence of spongin excludes the new species from this 

 genus. The specimen is probably mature, since there are several 

 embryos near the base of the sponge. 



Iotrochota baculifera Ridley, var. tumescens, var. nov. 

 (Plate XIII. fig. 1 .) 



Specimen forming an irregular flabellale and branching growth, 

 6 c.c. X 1 c.c. in area and - 3 c.c. in thickness. 

 Spicules. Styles averaging 210 x 10/;. 

 Strongyles 220-250 xlfi, with from one to three fusiform 



