REPORT ON THE MONAXONIDA. 69 



out into broad tufts, and their ends penetrate into the dermal layer and project very 

 slightly beyond the surface ; it is generally the pointed ends of the styli which thus 

 project. The peculiar arrangement of the spicular tufts along the edges of the pore- 

 bearing cracks has already been described. 



Spicules. — (a) Megasclera ; of one kind only, viz., styli (PI. XIII. fig. 18), very 

 nearly straight, tapering from near the middle towards both ends, and measuring about 

 07 by 0"019 mm. (b) Microsclera; these are enormously abundant, both in the dermal 

 membrane, including the pore-bearing areas, and in the deeper tissues. Three kinds 

 occur, all plentiful: — (l) Large palmate anisochelse (PI. XIII. fig. 17); especially 

 abundant in the dermal membrane, up to 0"072 mm. long, with the large end 0"019 mm. 

 broad. These chelate spicules are often found in very beautiful rosettes, which seem to 

 occur chiefly, if not solely, just beneath the dermal membrane. Numerous small 

 anisocheljB are also present, perhaps young forms of the large ones. (2) Numerous 

 sigmata (PI. XIII. fig. 11) of the usual shape, frequently much contorted, measuring 

 about 0'053 by 0*0024 mm. (.3) Trichodragmata (PL XIII. fig. 14), occurring in great 

 profusion in the deeper tissues, measuring about 0'076 by 0"013 mm. 



For further details as to the minute anatomy and histology the reader is referred to 

 the Introduction (Anatomy and Histology). 



This is one of the finest and most interesting sponges in the collection, and forms a 

 splendid example of the manner in which the pores may be collected into certain 

 definite " j^ore-areas," a phenomenon which has already been noted by SoUas^ 

 for other species of the genus Esperella. But we have here a still further development, 

 for not only are the pores, for the most part, definitely localised, but the grooves in 

 which they occur may be opened or closed by appropriate muscles, and thus the supply 

 of water regulated with great precision. The transverse muscle-fibres of the pore- 

 bearing cracks may be compared with the fibres which sometimes form sphincters 

 around the indiAddual pores ^ in other sponges. 



In the maeandering pore-areas and the almost stony spicular and non-reticulate dermis 

 this species stands markedly apart from all other described species, so far as they are 

 known to us ; the spiculation, on the other hand, as often happens in such cases, is of an 

 ordinary type. 



Locality. — Ofi" Port Jackson, 30 to 35 fathoms. One specimen. 



Esperella porosa, Eidley and Dendy (PI. XV. figs, 6, 9, 17 ; PI. XVI. fig. 5). 



188G. Esperella porosa, Ridley and Dendy, Ann. and Mag. Nat, Hist., ser. 5, vol. xviii. p. 338. 



Sponge (PI. XVI. fig. 5) cylindrical ; length of largest specimen about 50 mm. 



Diameter about 6 mm. Colour in spirit nearly white. Texture fibrous, but open and 



1 Vide Ann. and Mag. Nat. Hist., ser. 5, vol. ix. p. 437. 



' Ficfe Vosmaer, Bronn's Klass. u. Ordn. des Thierreichs, Porifera, p. 125. 



