REPORT ON THE TETRACTINELLIDA. 
301 
Jereopsis, applied to an apparently similar sponge obtained from the Gulf of Mexico, in 
water from 80 to 90 fathoms deepd Differences in detail, no doubt, exist between the 
desmas of the Fiji sponge and the Cretaceous SiphonisB ; in the latter they appear, for 
instance, somewhat smaller and not so freely branched as in the former. Such differences, 
however, are of no more than specific importance, and a generic distinction can only be 
maintained on the ground of our ignorance of some of the more important characters of 
the fossil forms, such for instance as the form of the microscleres and of the ectosomal 
megascleres. The dimensions of the sponge under description are as follows : — the total 
height is 46 mm., the diameter of the body 39 mm., the length of the pedicel is about 
15 mm., the size of the base 23 by 10 mm.; the excurrent canals are 1'5 mm. wide near 
their distal ends ; the incurrent canals 1 mm. and less where they commence at the surface. 
Family II. Corallistida:. 
Trisenophora in which the desma is monocrepid and tuberculated. 
Genus 1. Corallistes, 0. Schmidt. 
Corallistidse in which the ectosomal megasclere is a dichotrimne, and the microscleres 
are spirasters. The pores are simple. 
Corallistes typus, 0. Schmidt (PI. XXXIV. figs. 14-1 8a). 
Corallistes typus, O. Schmidt, Spong. Atlant. Gehiet., p. 22, pi. in. fig. 3, 1870. 
Corallistes howerbanld (pars), Carter, Ann. and Mag. Nat. Hist., ser. 4, vol. xviii. p. 460, 1876. 
„ „ „ Zittel, Abhandl. d. k. baier. Akad. d. Wiss., p. 103, 1878. 
Sponge (PI. XXXIV. figs. 14, 15). — A thick transversely oval plate with well-rounded 
edges, erect, attached by an expanded incrusting base. Oscules small, somewhat numerous 
on the convex side. Pores dispersed over the concave side, singly perforating the poral 
areas. The rounded margin of the sponge is devoid both of oscules and pores. 
Spicules. — I. Megascleres. 1. Desmas (PL XXXIV. fig. 16), these present the usual 
Corallistes form, and are studded with the characteristic capstan-shaped tubercles, as well 
as with simple conical and cylindrical forms ; the ends are expanded to form foliated 
plate-like processes, which adapt themselves to the sides and ends of neighbouring desmas. 
2. DichotriaBne (PL XXXIV. figs. 18, 18a), rhabdome short, conical, with rounded end; 
deuterocladi also with rounded ends, rhabdome from 0'238 to 0'32 by 0‘032 mm., proto- 
cladi 0‘02 mm., deuterocladi 0T16 mm. long. These spicules are of very various size, 
and the largest differ in the length of the rhabdome in different regions of the ectosome. 
* 0. Schmidt, Spong. Meerb. von Mexico, p. 20, pi. ii. fig. 10, 1879. 
