DENDY—REPORT ON THE CALCAREOUS SPONGES 15 
abundant in the narrow membranous collar which surrounds the vent, and by no means 
confined to the actual margin. 
The only histological feature that requires notice is the basal position of the nuclei 
of the collared cells in the spirit-preserved material. 
Previously-known Distribution. Tristan da Cunha (Poléjaeff). 
Register No., Localities, dc. cxvut., Salomon (Chagos Archipelago), 15 fathoms, 
10.6.05. 
7. Pericharax peziza* n. sp. 
(Plate 1, fig. 9; Plate 5, figs. 3, 4.) 
The single specimen (Plate 1, fig. 9) has the form of a shallow, thick-walled cup, the 
mouth of which is oval in outline. It has apparently been attached below to some 
foreign object, but there is no indication that it ever possessed a stalk. The mouth of 
the cup is obviously a greatly dilated osculum and is surrounded by a narrow, thin 
oscular margin, or collar. The outer surface of the cup is smooth, but appears minutely 
reticulate under a hand lens; the inner surface is perforated by the very numerous 
openings of the exhalant canals, which show but little tendency to grouping. 
The longer diameter of the sponge measures 37 mm., the shorter diameter, at right 
angles to this, about 29 mm. The depth of the cup internally is about 14 mm. and the 
maximum thickness of the wall about 7 mm. The thin oscular margin is under 2 mm. 
in width. 
The texture is firm but not very compact, and the colour in spirit pale wax yellow. 
The canal system minutely resembles that of P. heteroraphis, excepting for the 
enormous dilatation of the osculum, which finds a parallel, but in a still more exag- 
gerated condition, in Grantia labyrinthica. The gelatinous ectosome is about 0°26 mm. 
thick, and is broken up into trabecule by the small subdermal cavities, roofed over by the 
thin, pore-bearing dermal membrane and opening below into the large inhalant lacune. 
The ramifications of the inhalant lacunz roughly interdigitate with those of the exhalant 
lacunze, which open into the central gastral cavity. In the mesoglea between the two 
sets of lacunze are thickly scattered the spherical or subspherical flagellated chambers, 
each about 0°1 mm. in diameter. 
The arrangement of the skeleton is also identical with that found in P. heteroraphis, 
and the spicules are very similar, though for the most part a little smaller in average 
dimensions, as follows :— 
(1) Large triradiates of the main skeleton (Plate 5, fig. 3, a); equiangular and 
typically equiradiate; rays long, straight, slender and gradually sharp-pointed, measuring, 
say, about 1-4 mm. in length by 0:07 mm. in diameter at the base. 
(2) Small triradiates of the main skeleton (Plate 5, fig. 3, b; fig. 4, a); equiangular 
and typically equiradiate ; rays straight, slender and gradually sharp-pointed, measuring, 
say, about 0°18 by 0°015 mm. Intermediate sizes (Plate 5, fig. 3, c) between (1) and 
(2) occur in comparatively small numbers. 
* The specific name was suggested by the resemblance in external form to the fungus Peziza. 
