REPORT ON THE TETRACTINELLIDA. 
113 
Myriastra suhtilis, Sollas (PL XIV. figs. 23-28). 
Myriastra suhtilis, Sollas, Prelim. Account, Sci. Proc. Roy. Dubl. Soc., vol. v. p. 188, 1886. 
Sponge (PI. XIV. fig. 23). — Small, cylindrical, compressed, rounded above, produced 
into a few short rounded lobes below ; at the summit a few small oscules of different 
sizes, each leading into a deep cloacal tube, which receives several small cxcurrent canals. 
Pores in sieves, generally distributed over the surface. 
Flagellated chambers from 0’02 to 0‘036 mm. in diameter, with an apopyle from 
O'OliS to 0’016 mm. in diameter; aphodus short, about O’OIG mm. long, and of the 
same diameter as the apopyle ; sometimes absent, when the chamber becomes eurypylous. 
Spicules. — I. Megascleres. 1. Oxea (PI. XIV. fig. 24), fusiform, straight or slightly 
curved, ends variable, sharply or bluntly pointed, or rounded off, or somewhat mucronate, 
like a lead-pencil point ; 1‘33 to 1’51 by 0'0316 mm. 
2. DicTioirisene (PL XIV. fig. 25), with a straight conical rhabdome, pointed variably 
like the oxea, and bifurcated claclfi the protocladi projecting forwards, the deuterocladi 
extending horizontally. Ehabdome 1'16 to 1'33 by 0'04 mm., protocladi 0‘16 mm., 
deuterocladi 0’0413 mm. long ; chord 0‘4 mm. 
3. Anatrisene (PL XIV. fig. 26), with a straight, cylindrical, sharply pointed rhab- 
dome, and short, curved, sharply pointed cladi ; distal outline of the cladome nearly 
semicircular. Ehabdome 1*16 by 0'012 mm., cladi 0'04 mm. long, chord 0’06 mm. 
II. Microsclere. 4. Chiaster (PL XIV. figs. 27, 28), actines tylote, variable in 
number, frequently very numerous, rarely reduced to three or four ; from 0‘008 to 
0‘01 mm. in diameter; when reduced to a triradiate form, each actine 0'008 mm. in 
length. 
Co/owr.— Greyish-white. ' 
Habitat. — Kobe, Japan ; depth, 8 to 50 fathoms. 
Remarks. — Two specimens of this sponge are in the collection ; one fragmentary, 
and the other complete, the latter is 15 mm. high, 10 mm. and 11 mm. in breadth 
and width. At the summit are three oscules, the largest 1 mm. in diameter. The 
ectosome varies from about 0'18 to 0’32 mm. in thickness; it consists of collencbyme, 
which immediately below the outer epithelium passes in some places into a layer of 
darkly stained tissue containing numerous minute oval vesicles, about 0‘006 mm. in 
diameter, each containing an oval protoplasmic mass ; these cells become more densely 
crowded together as they are traced towards the exterior; elsewhere this tissue is 
replaced by a layer of fusiform cells, probable myocytes. In the midst of the ectosome 
occur small cell-like aggregates, about 0’012 mm. in diameter, consisting of minute 
homogeneous, spherical, deeply stained bodies, about 0’003 mm. in diameter ; these 
aggregates, the nature of which is problematical, occur in considerable numbers, 
(ZOOL. CHALL. EXP. — PART LXIII. — 1887.) Rrr 15 
