64 THE VOYAGE OF H.M.S. CHALLENGER. 



arrangement of the skeleton, the shape of the sj^icules, and the presence of only one kind 

 of microsclera, the last being a very remarkable point. Esperia stolonifera, Merejkowsky, 

 from the White Sea/ has a very similar spiculation, the stylus being, as here, not 

 tylote, but the anisochela is much narrower in that species than in Esperella 

 mammiformis and only about half the length. Lying in the soft tissues at the bases of 

 the specimens were a number of small, round, or sometimes hemispherical embryos, 

 which will be found described in the Introduction. 



It is noteworthy that the soft parts of the sponge contained a large number of 

 foreign bodies, such as Diatoms, &c. 



It appears that the sponge may sometimes live free on the sea-bottom, the base 

 being in these cases "j)inched up" (as represented on PL XIV. fig. 5) instead of flat 

 and expanded ; or possibly the sponge may have been attached to a very small object. 



Locality.— ^taiion 147, December 30, 1873; lat. 46° 16' 8., long. 48° 27' E.; east of 

 Prince Edward Island; depth, 1600 fathoms; bottom, Diatom ooze; bottom tempera- 

 ture, 34°'2. Six specimens, mostly much damaged. 



Esperella kqndiformis, Ridley and Dendy (PL XV. figs. 2, 10, lOa ; PL XVI. 

 figs. 2, 2a, 2h). 



1886. Esperella lapidiformis, Eidley and Dendy, Ann. and Mag. Nat. Hist., ser. 5, vol. x^'iii. 



p. 338. 



Sponge (PL XVI. fig. 2) massive, squarish, with rounded corners ; resembling 

 nothing so much as a water- worn boulder, whence the specific name. It has apparently 

 been attached by one corner, which is much frayed out. Length 131 mm., breadth 

 88 mm., thickness 69 mm. Colour in spirit yellowish-grey. Texture very soft and 

 yielding, but fibrous. Surface even, but minutely hispid. Dermal membrane thin 

 and transparent. Oscula (PL XVI. fig. 26, o) very distinct and characteristic, consisting 

 of numerous short, wide, tubular processes, scattered over the upjier end of the sjDonge. 

 The wall of each tube is thin and membranous, strengthened by very closely placed 

 spiculo-fibres, which, on approaching the free edge, break up into their component 

 spicules, which form a slight projecting fringe around the osculum. Average width of 

 osculum about 8 '3 mm. Length of tubular process about 6 '2 mm. There are about 

 twenty such oscula, and they are confined to the upper end of the sponge. Pores 

 distinct, very numerous, scattered irregularly over the surface of the sponge, so closely 

 placed as to reduce the dermal membrane to a network ; shape generally oval, 

 longest diameter about 0'15 mm. 



Skeleton. — {a) Dermal; absent, except in the tubular processes around the oscula, 

 as described above. (5) Main ; composed of an irregular, rather loose reticulation 



1 Mem. Acad. Sci. St. Pdcrsh., vol. xxvi. pt vii. p. 23. 



