OCR Text |
Show 1873.] DR. J. S. BOWERBANK ON THE SPONGIADcE. 331 fusiformi-acuate or subovo-spinulate, very large and long. Skeleton. spicula superfusiformi-acuate and subovo-spinulate, large and long- Tension-spicula superfusiformi-subovo-spinulate, small, irregularly dispersed, numerous. Colour, dried, light grey. Hab. Portland, Maine, N. America (Dr. Dawson, M'Gill's College, Montreal). Examined in the dried state. I received a small slice of this sponge from Prof. Dawson. From the curve of the surface, this specimen appears to have been about an inch and a half in diameter. In its present state the hispidation of the surface is very strongly produced, and probably much exaggerated by drying ; the spicula are comparatively very large and long-more so than those of the skeleton-fasciculi. The secondary series of defensive spicula are of the same form as those of the interstitial membranes, but not more than half their average size. The whole of the spicula are exceedingly fusiform, the middle of the shaft being frequently twice the diameter of the base of the spiculum. The ovo-spinulate character prevails more or less in all the spicula, but is more distinctly produced in those of the interstitial membranes and the secondary dermal defensive ones. In the deeply seated portions of the skeleton-fasciculi the ovo-spinulate character is very nearly or quite obsolete in some of the skeleton-spicula, and in others every gradation of its development may be traced up to its perfect production. No traces of reproductive organs could be detected on any part of the interstitial membranes. The peculiarities of the organization of this sponge distinctly separate it from any other species with which I am acquainted. DESCRIPTION OF THE PLATES. PLATE XXVIII. Isodictya mirabilis, Bowerbank. Fig. 1 represents the type specimen, natural size. 2. A small portion of a section at right angles to the dermal surface, magnified 80 linear. 3, 4. T w o of the short, stout acuate skeleton-spicula, magnified 123 linear. 5. One of the slender tension-spicula from the interstitial membranes, magnified 123 linear. 6. One of the inhalant pocilla, partially closed by the radial arrangement of conical sacculi, magnified 61 linear. 7. A section at rigbt angles to the dermal surface of one of the inhalant pocilla, magnified bl linear. 8. One of the conical sacculi of the inhalant areas, exhibiting the remains of a membrane, wbich probably occasionally closed the mouth of that organ, magnified 80 linear. PLATE XXIX. Dictyocylindrus dentatus, Bowerbank. Fig. 1 represents the type specimen, half the natural size. 2. One of the branches, natural size. 3. A side view of one of the dentato-cylindro-hexradiate retentive and defensive spicula from the dermal membrane, magnified 530 linear. |