Sponges from the Atlantic Ocean. 239 



discoloration, v:\wn phuccl umlcr the microscope, is found to 

 arise tVuiu tlu' jtrcsonco ot" sarcodc cliarircd witn two kinds of 

 spicules, viz. oui' skeleton- and one tlesh-spieule. Skeleton- 

 spicule aeuate, straight, but witli the large end suddenly bent 

 to one side (like the head of a walking-stick), and terminating 

 attenuatingly in a point at the other end, sparsely covered 

 with short vertical spines throughout, 80- bj 3-G0<>()ths inch 

 (PI. XV. fig. 43, a). Flesli-s])ieule a simple biliamate, much 

 curved, and more or less tortuous (Hg. 43, h). The skeleton- 

 spicules are sparsely imbedded among the Hcsli-spiculcs, which 

 are exceedingly numerous and thrown together confusedly, so 

 as to form the greater part of the mass (fig. 43, c). Pores 

 and vents not seen. Size of portion of discoloration in the 

 Corallistes about \ inch in diameter. 



Ilab. ^larine, on Coralli.stes Boicerhanhn. 



Loc. Station 25, in 374 fathoms, near Cape St. Vincent. 



Ohs. This sponge is chiefiy remarkable for the form of its 

 skeleton-spicule and the mass of bihamates in which it is 

 imbedded. Being parasitic among the spicules of Corallintes, 

 I, of course, can give no description of its form : I am not 

 quite certain that it should be called a Microciona, and there- 

 fore only give this generic name provisionally. 



Microciona jnisilla, n. sp. (PI. XVI. fig. 51, a, i, c, d.) 



I have met with another Microciona of the same kind, 

 growing on Polytrema utn'culare, not dredged up on board 

 the 'Porcupine' (xVnn. 1876, vol. xvii. p. 210), but probably 

 from the troj)ics. (Dr. Bowerbank has figured a similar 

 spicule from Oculina rosea, ap. cit. vol. i. pi. xi. fig. 243.) In 

 my instance, however, the skeleton-spicules are smooth, and 

 the bent portion of the large end has a tendency to a spiral 

 twist (a, h) ; while they grow erect on the surface of the 

 Polytrema, with fine acuates between them (c), and minute 

 bihamates (?) scattered throughout the structure, which are 

 almost too small to be satisfactorily described under a ^-inch 

 object-glass (</). The thick skeleton-spicule with bent large 

 end is hardly more than a quarter the size of that of Microciona 

 {ntejctii^i although somewhat similar in form, being about 36- 

 by l-6OU0ths inch in its greatest diameters. 



Phahellia ventilahrum, l^\i., = Jlalichondria v., Johnston. 



Fragments of this sponge appear in jars 61-63, 64, 65, and 

 84, which, being the numbers of the stations where they were 

 dredged up, indicate a depth varying between 155 and 640 

 fathoms, and a locality extending north of the Butt of Lewis to 



