OCR Text |
Show 1875.] SILICEO-FIBROUS SPONGES. 2/3 are three or more layers of the skeleton-structure. The fibres of the interior of the cup have the greatest number of spines upon them; those of the outer surface appear to be nearly spineless. The spines are acutely conical; their greatest height rarely exceeds their basal diameters. The fibres and the central canals within them both vary to a considerable extent iu their diameter. One of the largest fibres measured -^g hich and one of the smallest ji^- inch in diameter. The average of three that were measured was ^-g-g inch. One of the largest canals measured ^ u W m°b iu diameter; and a very small one in connexion with the large one was y ^ W inch, and the average j^j-j- inch in diameter. There does not appear to exist any definite proportion between the fibre and its central canal, a large canal frequently occurring in a small fibre, and a very slender one in a stout fibre. In their course through the skeleton they usually coalesce at each angle of the rete; but it not unfrequently occurs that large fibres have two canals running parallel to each other, as if each had originated at opposite angles of the rete ; and occasionally one or both terminate in a spherical dilatation. A few of the interstitial spicula fortunately remain entangled in the skeleton-rete. They are small, rectangulated, sexradiate forms, with smooth cylindrical radii, and are all of about tbe same size. Some portions of the skeleton-fibres were covered by a very thin layer of sarcode of a bark-brown amber-colour. The sponge was apparently a skeleton when brought up from the bottom of the sea; but although so many important characters are absent, those available are sufficiently striking to render its discrimination from other nearly allied species satisfactory. I have named the species after Dr. Gassiot, through whose kindness I have had the opportunity of examining and describing it. The specimens were dredged on the 22nd July, 1872, lat. 14° 8" N., long. 77° 38" W., 800 to 1000 fathoms; and Dr. Gassiot in his letter to me states, " Reliance can be placed on statement of locality, depth &c, as the specimens were put into bottles and marked by Capt. Hunter, who is a most energetic officer and careful observer. F A R R E A P O C I L L U M , Bowerbank. Sponge cup-shaped, contracted; pedicel short; parietes thin. Oscula, pores, and dermal membrane unknown. Skeleton siliceo-fibrous ; fibres cylindrical, furnished more or less with short acutely conical spines; rete more or less rectangulated, rather irregular; central canal very slender, often terminating abruptly in a czecoid manner. Internal defensive organs rectangulated sexradiate, rather large, based on the sides of the fibres; radii attenuated, abundantly spinous, and also furnished rather abundantly with rectangulated sexradiate spicula, small and slender; radii attenuating, incipiently spinous. Sarcode dark and opaque. Colour, in the dried state, very faint rose-pink. Hab. West-Indian seas (Capt. Hunter, B.N.). Examined in the dried state. PROC. ZOOL. Soc-1875, No. XVIII. 18 |