cxlviii 
THE VOYAGE OF H.M.S. CHALLENGEE. 
Geiras 2. Caminus, 0. Schmidt. 
Caminus, 0. Schmidt, Spong. Adriat. Meeres, p. 48, 1862. 
The sterraster is seldom spherical ; the somal microsclere is a spherule. The roofs of 
the incurrent chones are cribriporal, and the oscule is the patent opening of a cloaca. 
Type — Caminus vulcani, 0. Schmidt (p. 241). 
Genus 3. Fachymatisma, Bowerhank. 
Pachymatisma, Bowerhank, Mon. Brit. Spong., vol. ii. p. 3, 1866. 
The sterraster is subspherical or ellipsoidal ; the somal microsclere is a microstrongyle. 
The roofs of the incurrent chones are cribriporal, and the oscules are the single openings 
of cloacal chones, which each lead into a large cavity beneath the chonal sphincter 
(Fig. XIV., A). 
Type — Pachymatisma johnstonia, Bowerhank (p. 242). 
Subfamily 2. Geodina. 
The megascleres are rhabdi, ortho-, or dichotriaenes, and frequently in addition pro- 
and anatriaenes. The sterraster is spherical or ellipsoidal ; the somal microsclere is a 
polyactinose aster. 
Genus 4. Cydonium (Fleming). 
Cydonium, Fleming, History of British Animals, p. 516, 1828. 
„ Sollas, Ann. and Mag. Nat. Hist., ser. 5, "vol. v. p. 243. 
The incurrent chones are furnished with cribriporal roofs ; the oscules are sometimes 
uniporal, but more usually cribriporal, openings of excurrent chones which resemble the 
incurrent chones (Fig. XIY., b), but are usually collected in special areas without definite 
margins. 
Type — Cydonium mulleri, Fleming (p. 254). 
Genus 5. Geodia (Lamarck). 
Oeodia, Lamarck, Mem. Mus. Hist. Nat. Paris, vol. i. p. 333, 1815. 
Pyxitis, 0. Schmidt, Spong. Atlant. Gebiet., p. 70, 1870. 
Geodia, Sollas, Ann. and' Mag. Nat. Hist., ser. 5, vol. v. p. 245, 1880. 
,, Vosmaer, Bronn’s Klass. u. Ord. d. Thierreichs, Porifera, p. 317, 1887. 
The incurrent chones are furnished with cribriporal roofs. In the young Sponge the 
oscule is the patent opening of a cloaca, into which the excurrent canals open by 
