CALLOPEGMA. 61 



The only example of this species is a somewhat worn specimen from flint-gravel. 

 The canals in this specimen have been infilled with silica, and now project as so 

 many ridges down the sides of the sponge. The spicules have also disappeared, but 

 their moulds in silica are distinctly shown. 



This species may be distinguished from A. sulcifera by the greater number of the 

 vertical canals, also by their straight direction, and the larger size of the skeletal 

 spicules. 



Distribution. Gravel, Upper Chalk : Stanway, Gloucestershire. 



Genus CALLOPEGMA, Zitfel, 1878. 

 Callopegma Schlonbachi, Zitt. 



1878. Callopegma Schlonbachi, Zitt. Studien, II Ab. p. 75, t. 9. f. 1. 

 Detached skeletal spicules of this species. 

 Distribution. Upper Chalk: Ahlten, ^wao^er [ZitteVs coll.). 



Callopegma obconicum, Hinde, n. sp. (Plate XI. figs. 3, 3 «, 3 b.) 



Sponges small, inversely conical, apparently sessile. The upper surface is flat, or 

 even in some examples slightly convex ; the basal termination is obtusely rounded. 

 An average specimen is 20 mm. in height and 22 mm. in diameter. 



In the central portion of the summit are the apertures of several canals, about 

 2 mm. each in width, which extend downwards into the sponge ; there is also a 

 system of branching sinuous canals, seen in weathered specimens, which radiate from 

 the centre of the upper surface towards the sides of the sponge. The lateral surface 

 appears also to be furnished with minute pores. 



The spicular structure, as seen in a vertical section, is of an open, irregular 

 character. The arms or rays of the spicules are about "5 mm. in length. No 

 dermal layer has been preserved in the specimens. 



This species is usually preserved in the interior of flints, and the spicular structure 

 is seldom retained. In some instances, however, the spicules remain in the form 

 of iron peroxide. This form may be distinguished from Callojiegma acaule, Zittel *, 

 by its smaller size, the absence of a cup in the centre, and its even surface. 



Distribution. Upper Chalk : South of England. 



Callopegma ficoideum, Hinde, n. sp. (Plate XL figs. 4, 4 «, 4 b.) 



Sponges fig-shaped or subspherical, with flattened or slightly rounded summits, 

 and with one or more straight or curved peduncular projections at the base, and 

 occasionally slight nodosities on the surface. An average specimen is 60 mm. in 

 height and 50 mm. in diameter. 



• Studien, II Ab. p. 75, t. 2. f. 6 a. 



