262 
THE YOYAGE OF H.M.S. CHALLENGEK. 
Section 3. Ditriaena. 
Species without cortical oxeas, but with at least two forms of triaene. 
Cydonium arabicum, Carter. 
Geodia {Cydonium) arabica, Carter, Ann. and Mag. Nat. Hist. ser. 4, vol. iv. p. 4, pi. i. figs. 
9-16, 1869. 
Sponge . — Globular, free or fixed ; surface hispid. 
Spicules . — I. Megascleres. 1. Oxea, 2’85 by 0’0552 mm. 2. Orihotriaene, Th&hdiome 
3’88 by 0‘0966 mm. 3. Protrisene, rhabdome 5'83 by 0‘0414 mm. 4. AnatrisBne,dcdh- 
dome 5 ’14 by 0‘0277 mm. 
II. Microscleres. 5. Sterraster, ellipsoidal, O'll by 0'096 by 0'069 mm. 6. Spher- 
aster, with slender, cylindrical, truncate actines, 0’025 mm. in diameter. 7. Spheraster, 
with conical actines, having rounded ends, 0 '046 mm. in diameter. 
Colour. — Grey externally, yellowish within. Size, 75 mm. in diameter. 
Habitat . — South-east Arabia, north-east end of the island Masjie. 
Cydonium {?) pergamentaceum (0. Schmidt). 
Geodia ^ergamentacea, 0. ScEmidt, Spong. Atlant. Gebiet., p. 69, 1870. 
Sponge. — Parchment-like, hispid in places, cortex 0’25 mm. in thickness (0. Schmidt). 
Spicules. — I. Megascleres. 1. Oxea, 2'24 by 0’038 mm. 2. Ortho trisene, rhabdome 
1'6 by 0’032 mm., chord 0'533 mm. 3. Anatrisene, rhabdome 1’78 by 0'013 mm., 
chord 0'088 mm. 
II. Microscleres. 4. Sterraster, ellipsoidal, 0‘076 by 0'06 mm. 5. Othex Asters (?). 
Habitat. — Portugal. 
Remarks . — The measurements were obtained from a type-slide presented by Schmidt 
to the British Museum. Schmidt’s description is just two lines in length. 
Cydonium eonchilegum (0. Schmidt). 
Geodia concldlega, 0. Scbmidt, Spong. Adriat. Meeres, p. 51, pi. iv. fig. 11, 1862. 
Sponge. — Irregularly tuberose ; surface hispid in places, bearing attached fragments 
of shells and stones; cortex 1’79 mm. in thickness, chiefly composed of the sterrastral 
layer, ectochrote very thin. Pores in sieves overlying large incurrent chones ; oscules not 
distinguishable from the pores. 
Spicules. — Megascleres. 1. Oxea, 2 '32 by 0 ’03 2 mm. 2. Dichotrisene, rhabdome 
2’2 by 0'032 mm., protocladi 0’052 mm., deuterocladi 0‘135 mm. long. 3. Anatrisene, 
rhabdome 3‘93 by 0'013 mm., cladi 0'064 mm. long, chord O’l mm. 
