PLATE LXXXIII. 279 



TETHEA SPINOSA, Bowerbank, 

 Plate LXXXIII. 



Sponge massive, round or oval, sessile. Surface 

 smooth, and even. Oscula and pores inconspicuous. 

 Dermal membrane thin, pellucid, abundantly spiculous; 

 tension spicula acuate, as long as those of the skeleton, 

 but more slender, abundant, irregularly disposed ; 

 external defensive and retentive spicula attenuato- 

 cylindrical rarely or acuate, variable in size and form, 

 strongly spinous ; spines acute, few in number, irre- 

 gularly disposed, frequently longer than the greatest 

 diameter of the spiculum. Skeleton. Fasciculi multi- 

 spiculate, spicula acuate, long and slender. Interstitial 

 membrane sparingly spiculous ; spicula same as those 

 of the dermal membrane. Internal defensive spicula 

 the same as the external defensive ones. 



Colour. In the dried state, light ochreous yellow. 



Habitat. Fowey Harbour, Mr. C. W. Peach. 



Examined. In the dried state. 



I am indebted to my kind friend Mr. C. "W. Peach 

 for the two fragments of the sponge which are figured ; 

 they are the only specimens of the species with which 

 I am acquainted. From the direction of the converging 

 fasciculi of the skeleton from the external surface in- 

 wards, in both the fragments, they have the appearance 

 of having belonged to a spherical or oval mass rather 

 exceeding two inches in diameter, and the curvature of 

 what remains of the dermal surface is in favour of the 

 same idea; and as the prevailing form of the other 

 known species of Tethea are in accordance with similar 

 shapes, I have taken the characters of form in this 

 species as granted ; but whether this supposition be 

 correct, or the contrary, is of very little importance, as 

 the structural characters are so distinctly different from 

 those of any other known species of Tethea, that a 

 careful examination of them cannot well fail of leading 

 the student to a correct discrimination of the species. 



