250 
THE VOYAGE OE H.M.S. CHALLENGEE. 
sisting chiefly of the sterrastral layer ; ectochrote thin, traversed by numerous hispidating 
cortical oxeas. 
Spicules. — I. Megascleres. 1. Somal oxea, 3’2 by O’OoS mm. 2. Co^-tical oxea, 
0‘33 to 0'5 by 0'006 mm. 3. Orthotrisene, rhabdome 3’25 by 0'08 mm., cladi 0’4 mm. 
long. 4. Protrisene, rhabdome fusiform, 4‘0 mm. long and probably over, by 0‘0193 
mm. near the cladal origin, and 0'0258 mm. where thickest, cladi 0’206 mm., chord 
0'143 mm., sagitta 0'191 mm. ; rhabdome sometimes produced 0‘08 mm. beyond the 
cladal origin. 5. Anatrisene, rhabdome cylindroconic, often strongylate, 4’5 by 0'025 
mm., cladi 0‘16 mm., chord 0'143 mm., sagitta 0‘122 mm. 
II. Microscleres. 6. Sterraster, spherical, 0'064 mm. in diameter. 7. Somal 
spheraster, actines minute, short, cylindrical, strongylate ; 0’013 mm. in diameter. 8. 
Choanosomal oxyaster, actines conical, not numerous, a single actine 0’0258 mm. long. 
9. Subcortical (?) spheraster, a well-marked centrum and somewhat numerous, stout 
cylindrical actines, spined near the ends and truncate. 
Size, 213 mm. long by 113 mm. broad ; another specimen 69 mm. in thickness. 
Habitat . — Honduras and Jamaica. 
Geodia barretti, Bowerbank. 
Geodia Barretti, Bowerbank, Phil. Trans. Eoy. Soc., p. 279, 1858 ; Ibid., pi. xxxii. fig. 2, 1862 ; 
Mon. Brit. Spong., voL i. pp. 168, 171, pi. xxviii. fig. 354, 1864; Proc. 
Zool. Soc. Lond., p. 198, pi. xi. 1872, 
Cydonium Barretti, Gray, Proc. Zool. Soc. Lond., p. 548, 1867. 
Geodia Barretti, Sollas, Ann. and Mag. Nat. Hist., ser. 5, vol. v. p. 241, pis. x.-xii., 1880. 
Geodia Barretti, Vosmaer, Sponges of the “ Willem Barents,” p. 23, pi. iii. figs. 50, 51, pi. iv. 
figs. 120-122, 1881. 
Sponge. — Spherical when young, with a single oscule with inflected margin leading 
into a deep cloaca, into which the excurrent canals open by sphinctrate mouths through 
walls w^hich resemble the cortex in structure ; massive and sessile when of larger growth, 
with one or more oscules, which are the patent openings of a wide shallow cloaca. Cortex 
0'6 mm. (B.), and 0’4 mm. (S.) thick, with a well-developed ectochrote 0'238 mm. (B.), 
0'075 mm. (S.) thick, traversed by cortical oxeas which hispidate the surface; sterrastral 
layer 0’318 mm. (B.), 0'250 mm. (S.) thick, and inner fibrous layer 0’075 mm. (S.) thick. 
Spicules. — I. Megascleres. 1. Somal oxea, 3‘6 by 0'058 (B.) to 3‘6 by 0'071 mm. 
(S.). 2. Cortical oxea, 0‘387 mm, in length (B.), 0'387 by O’Ol mm. (S.). 3. Dichotrixne, 
rhabdome 41 by O'l mm, (B.), 2‘3 by 0’071 mm. (S.) ; protocladi 0'286 mm., deutero- 
cladi 0'32 mm, long (B.), chord 0'61 mm. (S.). 4. Anatrixne, rhabdome 4‘46 by 0'013 
mm. (B.) by 0‘0145 mm. (S.); cladi 0167 mm., chord 0'116 mm. long (B.), cladi 0‘13 
mm., chord 0'08 mm. long (S.), 5. Protrisene. 
II. Microscleres. 6. Sterraster, spherical, 0'064 and 0‘077 mm, (B.), 0'070 and 
