DENDY—REPORT ON THE CALCAREOUS SPONGES 13 
homoraphis and the other heteroraphis. My examination of the type specimens in the 
British Museum collection has led me to the conclusion that not only are these two 
so-called varieties specifically distinct, but that var. heteroraphis alone belongs to the 
genus Pericharax, the other being probably a Leucetta, without the characteristic dermal 
spicules of Pericharac. 
The genus has not been recorded since it was first described, but the rediscovery 
by the “Sealark” of P. heteroraphis, and of a new species closely related to it, in the 
Indian Ocean, and the careful study of these forms, has led me to accept the genus 
as a valid one and to characterize it as above. The position assigned to the genus, in the 
family Leucascidee, is justified not only by the character of the skeleton, composed mainly 
of equiangular and irregularly scattered radiates, but also, as in the case of Leucetta, by 
the basal position of the nuclei of the collared cells. 
6. Pericharax heteroraphis Poléjaett. 
(Plate 1, fig. 8; Plate 5, figs. 1, 2.) 
Pericharax cartert var. heteroraphis Poléjaeff [1883 |. 
The single specimen in the collection (Plate 1, fig. 8) agrees very well with the 
description and figure of the external form of P. carteri given by Poléjaeff. It is almost 
globular and about 20 mm. in diameter. There is a single vent about 4 mm. in diameter, 
with a slightly prominent oscular margin; and the sponge has apparently been attached 
by the lower pole, opposite to the vent. The surface is smooth, and covered by a thin, 
pore-bearing dermal membrane which, under a pocket lens, exhibits a beautifully 
reticulate appearance. The texture is firm and compact, and the colour in spirit pale 
greyish yellow. 
The large central cavity, which opens to the exterior through the osculum, is 
surrounded by a wall about 4 mm. thick, but gradually diminishing in thickness towards 
the oscular margin. The inner surface of this wall is pierced by numerous exhalant 
apertures, for the most part grouped in depressions. 
There is a well-defined, gelatinous ectosome, about 0°26 mm. thick. This layer 
contains no flagellate chambers, but is broken up into trabecul, running vertically to 
the surface, by the numerous small subdermal cavities, which are roofed over by the 
thin, pore-bearing dermal membrane. The subdermal cavities open collectively into large, 
irregular inhalant lacunz, which ramify inwards. Similar exhalant lacune, ramifying 
in the opposite sense, open into the large central cavity. In the mesoglea between the 
exhalant and inhalant lacunze lie the spherical or subspherical flagellate chambers, thickly 
scattered, and each about 0°12 mm. in diameter. 
The main skeleton consists of triradiate spicules, of two chief and very different 
sizes, scattered thickly and without order throughout the chamber layer of the sponge, 
the small spicules occupying the interstices between the large ones. 
There is a well-developed dermal skeleton, composed of a dense reticulation of small, 
tangentially placed triradiates, the rays of which frequently lie parallel and in juxta- 
position with one another to form multispicular meshes, continued below into the 


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