REPORT ON THE TETRACTINELLIDA. 
345 
at right angles to its surface, 0’17 mm. in diameter, immeasurably thin, crepis 0'04 mm. 
in length, when a stalk-like process is present, its diameter does not exceed 0‘008 mm. 
II. Microscleres. 4. Somal microxea, fusiform, slightly curved, surface minutely 
roughened, 0'055 by 0'004 mm. 5, Choanosomal amphiaster, a slender, straight axis, 
and a whorl of several slender, hair-like actines near each end, total length O’OllS mm., 
length of a single actine about 0‘004 mm. 
The microxeas are distributed tangentially in a layer beneath the outer epi- 
thelium, overlying the layer of discs ; they also extend throughout the sponge in such 
numbers as to constitute almost as considerable a part of the skeleton as the desmas. 
The amphiasters appear to occur only in the choanosome, and are not abundant even 
there. 
Colour. — Yellowish-grey in spirits. Size, 35 mm. in height by 25 mm. in maximum 
diameter. 
Habitat. — Locality not given by Schmidt; the sponge bears a label “Ag. 79, 134,” 
and the bottle a metal foil with the number 255. 
Remarks. — The skeleton of this sponge is the loosest and most fragile of all the 
Lithistids, and no species probably is better fitted for minute histological examination, 
unless possibly Discodermia dissoluta. It was to be expected that thin slices would 
furnish interesting results, but unfortunately the soft parts of the specimen are not 
sufficiently well preserved to exhibit structure. 
Neojpelta imperfecta, 0. Schmidt. 
Neopelta imperfecta, O. Schmidt, Spong. Meerb. Mexico, p. 88, pi. ix. fig. 11, 1880. 
Sponge. — Small, papilla-hke, compressed at the upper end, and produced into small 
oscular tubes. Longitudinal canals visible beneath the surface, running the whole length 
of the sponge. Pores simple (one measured 0'065 mm. in diameter). 
Spicules. — I. Megascleres. 1. Desma, epirabd smooth, more or less straight, or curved, 
or triradiate, crepidial axis 0‘04 mm. in length, zygosis by rounded tubercles, chiefly 
terminal. 
2. Disc, more or less oval in outline, margin entire or lobate, sometimes notched by 
a rhabdal sinus, under surface impressed by the underlying discs ; maximum diameter 
0‘35 mm. Crepidial strongyle either wholly or partly immersed in the disc, when only 
partly immersed projecting as a shaft from the lower surface. Crepidial axis from 0'04 
to 0‘087 mm. in length. 3. Rhahdus {?). 
II. Microscleres. 4. Microxea, fusiform, sharply pointed, smooth, slightly curved, 
0’07l by 0'004 mm. 5. Amphiaster, small, actines few, 0’0118 mm. in length. 
Colour. — Dark-brown. Size, the largest specimen is 10 mm. in length, by 4 mm. 
(ZOOL. CHALL. EXP. — PABT LXIII. — 1887.) Rrr 44 
