62 THE VOYAGE OF H.M.S, CHALLENGER. 



Family III. Desmacidonid/E. 



Megasclera of various forms, usually monactinal. Microsclera always present and 

 always including chelge.^ 



Subfamily 1. Esperellin.-e. 



188G. Egperina, Ridley and Dendy, Ann. and :Mag. Nat. Hist., ser. 5, vol. xviii. p. 337. 

 Skeleton fibre not echinated by laterally projecting spicules. 



Genus Esperella, Vosmaer (Pis. XIIL, XIV., XV., XVI.). 



1833. Ef'peria, Nardo, Isis, p. 522. 



1869. Raphiodenna, Norman, Brit. Assoc. Eep. for 1868, p. 333. 



1874. Raphiodesma, Bowerbank, Mon. Brit. Spong., vol. iii. pp. 94, 235. 



1885. Esp)erella, Vosmaer, Bronu's Klass. u. Ordn. d. Thierreiclis, Porifera, p. 353. 



Shape various, amorphous or symmetrical. Megasclera all monactinal, usually styli, 

 but sometimes with slightly developed, oval heads ; smooth. Microsclera palmate aniso- 

 chelae, to which may be added either sigmata, trichodragmata, small isochelse^ or toxa, or 

 combinations of these. Fibre usually distinct, branching and anastomosing, often 

 containing much spongiu. 



The name Esperia, which has so long been in use for this genus, was altered by 

 Vosmaer {Joe. cit.), to Esperella, because he found that it had already been given to a 

 genus of Lepidopterous Insects. 



Many species of the genus Esperella attain a high degree of complexity both as 

 regards spiculation and the arrangement of the soft parts ; a very characteristic feature, 

 though it perhaps hardly deserves a place in a generic diagnosis, is the breaking up of 

 the main fibres of the skeleton as they approach the surface of the sjjonge into brushes 

 of separate spicules which support the dermal membrane. 



The canal system is usually very complex and the pores are sometimes collected into 

 definite " pore-areas," although they may at the same time occur scattered on other parts 

 of the sponge. 



The Challenger dredgings have brought to light several very remarkable species of 

 this genus, but by far the most remarkable is the one which we have called Esperella 

 hiserialis, obtained at two stations in the South Pacific at depths of 2385 and 2250 

 fathoms respectively. This species has the external form of a Cladorrhiza, but with a 

 distinctly bilateral symmetry ; while the anisochelate microsclera, though exceedingly 



1 We liave incluileJ one or two species without clieljo on the supposition that they have had them and suljsequently 

 lost them. 



" "Very possibly only young forms of the anisochete, vide Carter, Ann. and Mag. Nat. Hist., ser. 4, vol. xiv. p. 102. 



