REPOET ON THE TETEACTINELLIDA. 
83 
The microxeas are scattered in considerable numbers through the collenchyme, but 
are not abundant enoua;h to form a felt. 
Spongin. — Where the large spicules touch each other they are sometimes united by a 
small quantity of spongin, which is developed around the point of contact. When the 
spicules are separated from each other the spongin remains adherent to one of them in 
the form of a little cup ; several such cups are sometimes to be met with on one and the 
same spicule (PI. IX. fig. 28). 
Pcecillastra crassiuscula, Sollas. 
Normania crassiuscula, Sollas, Prelim. Account, Sci. Proc. Eoy. Dubl. Soc., vol. v. p. 185, 1886. 
Sponge. — A thick vertical plate, outer incurrent face even, ending sharply above along 
a well-marked linear edge ; inner excurrent face rounded ofi' above against the incurrent 
edge : raised into rounded eminences, each bearing a single oscule. Both surfaces 
sparingly hispid. Incurrent canals running more or less vertically upwards to terminate 
in the patent oscules. Pores distributed in sieve-like areas over the origin of the incurrent 
canals, which cross the sponge wall more or less transversely. 
The flagellated chambers measure 0‘0355 by 0‘0395 mm. in length and breadth. 
Spicules. — I. Megascleres. 1 . Oxea, stout, fusiform, not sharply pointed, straight 
or more usually curved, 2'856 by 0’058 mm. 
2. Ortliotrisene, with conical somewhat sharply pointed rhabdome and cladi, 
rhabdome not much longer than the cladi, both of about the same diameter. Rhabdome 
0‘678 mm., cladi 0'607 mm. long, both 0'0387 mm. in diameter. 
3. CaMrops, of the usual form, one actine 0'65 by 0‘048 mm. Both this and the 
orthotrisene comparatively rare. 
II. Microscleres. 4. Microxea, slender, straight, or gently curved, 0T36 by 0 ’00395 
mm. 
5. Metaster, numerous, frequently reduced to a plesiaster with four actines. One 
actine of a tetractinose plesiaster measures 0’0198 by 0’00197 mm. 
6. Spiraster, numerous, spire with several turns, spines numerous, total length 
0’0197 mm., length of a single spine 0’004 mm. 
Colour. — Greyish- white. 
Habitat. — Porto Praya, St lago ; depth, 100 to 128 fathoms. 
Remarks. — Both in general character and minute anatomy this sponge closely 
resembles Pcecillastra schulzii, the chief difference lying in the longitudinal course taken 
by the excurrent canals in the present species. It is represented by a single fragmentary 
specimen, which is perfect, however, as regards the upper margin, the basal part being 
that which has disappeared. It measures 19 mm. in height, 10 to 14 mm. in thickness, 
and 30 mm. in width, but was wider when complete. 
