PLATE XOII. 347 



it 8j)lunctrella horrida, C. Schmidt, but I have not 

 been able to ascertain wlietlier it lias yet been 

 described or figured. I have, therefore, thought it 

 advisable under all these circumstances to separate the 

 British species from Hymeniacidon, and to construct a 

 new genus for its reception under the designation of 

 Battersbyia, in acknowledgment of the good services 

 rendered to science by my friend Dr. Battersby, to 

 whom I am indebted for my first knowledge of the 

 British species, and I propose the following as the 

 generic character. 



Battersbyia, Bowerhanh. 



Skeleton. — A somewhat regular complication of 

 spiculated triradiate, and biangulated quadriradiate 

 siliceous spicula. 



The two forms of spicula are of about the same 

 relative size, and they are mixed in the skeleton struc- 

 ture in quite an irregular manner. From the various 

 positions of the two forms in the skeleton, they are 

 not always readily to be distinguished from each other, 

 but as I have stated in vol. ii, p. 227, " they may 

 always be determined by the fact that, in the spicu- 

 lated triradiate form, the central canals at their 

 junction at the middle of the spiculum form three 

 angles of each about 120°, and three others which 

 are right angles, while those of the biangulated quadri- 

 radiate spiculum form four right angles only at their 

 junction at the centre of the spiculum, as represented 

 in Plate XXXVIII, fig. 12, in the present volume. 



Hymeniacidon Aldousii, Bowerlanl. 



Plate XCII. 



Sponge massive, sessile. Surface smooth. Oscula 

 simple. Pores inconspicuous. Dermal membrane 



