PLATE LXXXIII. 279 



Tethea spinosa, Boiverhank. 

 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, fevf 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. Yf . Peach. 



Examined. — In the dried state. 



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

 for the tw^o fragments of the sponge which are figured ; 

 they are the only specimens of the species -Rath v^hich 

 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 distinctlj^ 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. 



