198 TRANSACTIONS LIVEEPOOL BIOLOGICAL SOCIETY. 



or without dermal crust of oxea. Chelae may be present. 

 Note. The orginal diagnosis runs: " Desmacidonidae 

 with a skeleton composed of dense bundles of slender 

 oxea, with very litttle spongin ; echinated by spined 

 styli." I have altered the diagnosis slightly in order 

 to include the undermentioned species. Topsent 

 created a new genus (Leptosia) for Bowerbank's ■ 

 Hymedesmia zetlandica, but I think we can include 

 that species under the present genus. 

 Clathrissa perarmata, B., XXXI. 

 „ trunca, B., 4, XI. 



„ zetlandica, B., XXIX. 



Genus Ophlitaspongia, Bowerbank. 

 Skeleton formed of horny fibres, not cored by spicules, 

 but echinated by smooth styli. Microscleres toxa. 

 Ophlitaspongia papilla, B., LXX. 



,, seriata, Grant, LXV. 



Genus Diplodemia, Bowerbank. 

 Skeleton formed of horny fibres containing smooth oxea 

 and echinated by smooth oxea. No microscleres. 

 Diplodemia vesicula, B., LXX. 



Genus Plocamia, 0. Schmidt. 

 Characteristic megascleres dumb-bell shaped spicules, 

 spined. Chief megascleres styli or subtylostyli, often 

 spined at their bases, sometimes accompanied by shorter 

 and more completely spined spicules. Ectosome some- 

 times with diactinals. Microscleres : isochelse and, 

 usually, toxa. 



Note. Topsent {20, p. 17) includes this genus under 

 his new sub-family Bubarince. But as that sub-family 

 is at present not yet quite satisfactorily defined, we 

 may be allowed to leave Plocamia amongt the 

 Ectyonince. The type of Topsent's new sub-family 

 is Bubaris, Gray. But as the same is supposed to 



