Sponges from the Atlantic Ocean. 317 



or fibula, C-shaped, simple, 4^-6000th9 inch long (fig. 12, o); 

 3, fiiu* acerates in buiidles, wliich represent tlic tricurvates, 

 17-()0()0tli.s inch long (fig. 12, ;>, 7). The skeleton-spicules 

 make up the general structure, and almost entirely that of the 

 stem and its branches, wliile the iiesh-spiculess are scattered 

 throughout the sponge generally. Hi^e of the most perfect 

 specimen 2^ inches higli by 1^ inch in transverse diameter; 

 largest part of the stem at the base -} inch in diameter. 



Hah. Marine. 



Loc. Atlantic Ocean in 345 fathoms, at station 65, about 

 40 miles N.N.W. of the Shetland Islands. 



Obs. There arc three specimens of this sponge, viz. two 

 in one jar and one in the other, unaccom})anied by any other 

 sponge. Both jars are labelled ^'65," which gives the loca- 

 lity and depth above mentioned. In its spicules it does 

 not ditier much from the forms most common to the group 

 Esperina ; but the presence of the plates and the cribriform 

 grooves between them, as above described, gives it a distinctive 

 scale-like character; hence the designation " placoides.^^ The 

 scales are not imbricated, but separate and arranged like slabs 

 of stone in a pavement with a groove between them, although 

 probably susceptible of being drawn together by general eon- 

 traction when the closure of the pores becomes necessary. 

 From the expanded and flattened state of the end of the stem 

 it would appear that the sponge had been attached to some 

 hard submarine object, growing erect perhaps, as the dredge 

 could not have reached it if it had been suspended from the 

 roof of a submarine rock-cavern. The specimens are charged 

 with spherical ova, whose largest size measures 25-1800ths 

 inch in diameter, and in many instances are sufficiently deve- 

 loped to present the rudimentary forms of the spicules of the 

 sponge to which they belong. 



Esperta borassus, n. sp. (PI. XIII. fig. 13, and PI. XV. 

 fig. 33.) 



So called from the groups of spicules of which it is com- 

 })Osed resembling so many minute palmyra trees in a row. 

 The head of each, windmill-like and supported on a stem 

 formed of a bundle of spicules, consists of the usual forms 

 common to Esperia, viz. a sub-pinlike fusiform skeleton- 

 spicule (PI. XV. fig. 33), and three forms of flesh-spicules, 

 viz. the usual ^*«equianchorate, separate and in rosettes 

 (PI. Xlll. fig. 13, c), the bihamatc or fibula (fig. 13,^), and 

 the tricurvate or bow, which is here represented as usual in 

 Espen'a, viz. in navicular or sheaf-shaped bundles of minute 



