Sponges from the Atlantic Ocean. 247 



sents a cribriform structure over the rounded cavities beneath 

 (fig. 29, a). Pores making up the cribriform area just men- 

 tioned (fig. 29, a). Vents scattered. Internal structure 

 becoming cavernous towards the base (fig. 30), charged with 

 the spicules of the species, and permeated by the excretory- 

 canals, of which the dilated cavernous structure is chiefly 

 composed. Spicules of two kinds, viz. skeleton- and flesh- 

 spicules. Skeleton-spicules of two forms, viz. : — 1st, the 

 largest, smooth, stout, slightly curved, acuate, rather abruptly 

 pointed, average largest size 40 by 1^ -1800th inch in its 

 greatest diameters (PL XV. fig. 41, b) ; 2nd, smooth, nearly 

 straight, slightly fusiform, constricted and slightly inflated at 

 the extremities, average largest size 20 by -}-1800th in its 

 greatest dimensions (fig. 41, a). Flesh-spicules of two forms, 

 viz. tricurvate and equianchorate. Tricurvate long, bent upon 

 itself so as to assume the form of a pair of forceps (PI. XIV. 

 fig. 32, a) (whence its designation) : arms separate at the 

 point of bending (which is round), but in contact a little further 

 on, and then spreading out again for a short distance towards 

 their terminations, which are unequal, one arm being a little 

 longer than the other; arms incipiently spined throughout, 

 spines recurved or inclined towards the bend on each arm, 

 becoming almost obsolete at the bend itself; extremities much 

 attenuated and finely pointed; average largest size 30 by 

 ^-1 800th of an inch in its greatest diameters. Equianchorate 

 (fig. 31, «, b) stout, consisting of a curved shaft and three linear 

 arms at each end ; the tubercle evident, and the falces re- 

 spectively extending to about half the length of the arm ; 

 average largest size 13 by 4-6000ths of an inch in its greatest 

 diameters, viz. the length of the shaft and width of the head 

 respectively. Size of entire specimen If long, 1^ wide, and 

 ^ inch high or thick, vertically. 



Hob. Deep sea. 



Loc. Atlantic Ocean. Between the north of Scotland and 

 the Faroe Islands. 



Obs. This specimen is alone in a jar with the No. " 54 " on 

 it, which gives a depth of 363 fathoms. It has already been 

 described among the British sponges by Dr. Bowerbank under 

 the name above given (vol. ii. p. 244), but not illustrated. 

 The " bidentate spicules " mentioned by Dr. Bowerbank 

 appear to me to be merely early forms of the equianchorate, 

 and the " minute bihamates " embryonic forms of the tri- 

 curvate or large forcipiform spicules, which, in the deep-sea 

 specimen are not more than 2-1800ths inch long, very faintly 

 displayed, very abundant, and with arms in all of unequal 

 length, the short one being not more than one third of the 



