OCR Text |
Show 560 DR. J. S. BOWERBANK ON [Nov. 2, traces of any pedicel. In every anatomical character it is in close accordance with the type specimen. A portion of this specimen is is quite obscured by a crowd of Foraminifera and Polycistina entangled in the areas of the skeleton-rete. The decease of m y friend Mr. Deane does not allow of m y determining the locality of this species with certainty; but I am strongly of opinion that it was collected by Captain Hunter in the West Indies, along with Farrea Gassioti and other similar specimens. FARREA SPINULENTA. (Plate LXI. figs. 2 & 3.) Sponge-mass unknown. Dermis furnished with a quadrilateral siliceo-fibrous network, armed at the angles oppositely externally and internally with imbricated elongate-conical spicular defences. Fibre solid, without canals, minutely spinous; spines acutely conical, rather numerous, symmetrically disposed. Dermal membrane thin, translucent, abundantly furnished with spinulo-quadrifurcate sexradiate stellate retentive spicula dispersed. Interstitial spicula large, simple, rectangulate, sexradiate; radii acerate, more or less spinous. Sarcode light brown. Colour, in the dried state, light brown. Hab. Tripoli (Captain C. Tyler). Examined in the dried state. The portion of the sponge representing this very interesting species is not quite the eighth of an inch in diameter. It was presented to m y friend Captain Charles Tyler by Mr. Deane. It was found off the coast of Tripoli. The specimen is but a minute portion of the dermis of a sponge the mass of which is unknown to us ; but the nature of the structures displayed by its microscopical examination unmistakably indicates that it belongs to the genus Farrea. The quadrilateral siliceo-fibrous network of the dermal rete accords in form very closely with that of Farrea occa. The fibres in each species are solid ; and, as in F. occa, the angles of the tissue, both externally and internally, are armed with imbricated conical spicular defences ; but these organs are longer and more slender in their proportions than in those of F. occa. Thus far they agree very closely in their structures. They differ from each other in other important characters. The fibres in F. occa are quite smooth, while those in the species under consideration are regularly and systematically spinous, forming a very important specific character. These spines are not irregularly dispersed; they are disposed in equidistant parallel lines, iu accordance with the long axis of the fibre, the spines in each line being also at about equal distances from each other and opposite the middle of the intervening spaces of those in the lines on each side of them, so that their mode of disposition on the fibre is remarkably symmetrical and very characteristic. Other essential differences occur in the dermal membranes of the two species. In the quadrilateral, smooth, siliceo- fibrous network of the dermis of F. occa, described in the Proceedings of the Zoological Society of London for March 13, 1869, |