REPORT ON THE TETRACTINELLIDA. 
89 
shaped strongyles lie transversely to the hispidating spicules, in the walls of the cloacal 
tube. It does not appear quite certain that they are proper to the sponge. The 
characters of the oscules clearly distinguish this sponge from Pcecillastra, and, recog- 
nising this, I substituted a new genus, Vulcanella, to receive it. Subsequently I came 
to recognise the similarity in the characters of its oscules and those of SpJiinctrella, 
0. Schmidt ; and as it was upon these very characters that Schmidt seized on founding 
his genus, there can be but little doubt as to the identity of Vulcanella and Sphinctrella ; 
on the other hand, the species Sphinctrella eribrifera and Sphinctrella horrida appear 
to differ considerably in form and general characters. 
Sphinctrella gracilis, n. sp. (PI. XLII. figs. 1,2). 
Sponge, incrusting. Oscules large, circular, surrounded by an erect fringe of long 
oxeas, closed by a thin membrane resembling a velum. Pores (?). 
Spicules. — I. Megascleres. 1. Oxea, stout, fusiform, straight or curved, sometimes 
irregularly bent, not sharply pointed ; 3'8 by 0‘1 mm. 
2. Oxea, long, slender, cylindrical, sharply pointed, straight or curved ; 5 '6 and over 
by 0'015 mm. 
3. Calthrops, seldom quite isoactinate ; actines conical, pointed, 0'83 by 0'064 mm. 
II. Microscleres. 4. Microxea (PI. XLII. fig. l), fusiform, slightly curved, sharply 
pointed, surface raised into an irregular spiral ridge or a succession of annular ridges, for 
the middle one-third or two-thirds of its length ; 0'35 by 0'0115 mm. 
5. Microxea, fusiform, slender, sharply pointed, smooth, curved, usually somewhat 
suddenly bent in the middle, 0'14 by 0'004 mm. 
6. Spiraster (PI. XLII. fig. 2), small, slender, spire of two complete revolutions, 
spines very small and slender, total length 0’015 mm. ; of a single spine 0'004 mm. 
7. Metaster, small, axis short and straight, 0'004 mm. long; spines 0‘012 mm. long. 
Colour (?). — The sponge is overgrown by some species of Monaxonid, of a black colour, 
which masks that of the Sphinetrella. 
Habitat. — St. lago, Porto Praya, Cape Verde Island, August 1873 ; depth, 100 to 
128 fathoms. 
Remarhs. — This sponge occurs incrusting a specimen of Corallistes masoni', it measures 
about 25 by 30 mm. in length and about 4 or 5 mm. in thickness ; three oscules are 
present, each from two to three millimetres in diameter, they closely resemble the oscules 
of the preceding species, but the membrane lining the shallow cloaca presents a com- 
paratively large central aperture. Possibly the sponge is not fully grown and additional 
apertures may appear with age. The annulated microxea bears a close resemblance to 
that of Sphinetrella horrida, 0. Schmidt [vide p. 100), with which indeed the present 
species may prove identical. The presence of this spicule distinguishes the present species 
(zooL. CHALL. EXP. — PART Lxiii. — 1887.) Rrr 12 
