776 PROF. A, DENDY AND MR. R. W. H, ROW ON 



For illustrations of tliis genus see Haeckel [1872]. 



The very peculiar character of the skeleton of the gastral cortex 

 seems to justify the erection of a new genus for 0. Schmidt's; 

 Leuconia stylifera. 



The only known species is: — 



1. L. STYLIFERA 0. Schmidt. 



Leuconia stylifera O. Schmidt [1870]. 

 Leucandra stylifera Haeckel [1872]. 



Genus 38. Aphroceras Gray [1858]. 



Diagnosis. Sponge usually a single person or a colony of such 

 persons in which the component individuals are readily re- 

 cognisable. Canal system sylleibid or leuconoid. Skeleton 

 of the chamber layer more or less confused, but frequently 

 with vestiges of an articulate tubar skeleton in the form of 

 subgastral or other sagittal radiates. Dermal skeleton of 

 tangentially placed triradiates supplemented by colossal oxea 

 placed longitudinally and not projecting from the surface 

 sufficiently to render it hispid. 



For illustrations of this genus see von Lendenfeld [1891], 

 under Vosmaeyna corticata. 



The genus Aphroceras was originally proposed by Gray [1858] 

 to receive a sponge from Hong-Kong, whose chief characteristics,, 

 at any rate from our point of view, were the leuconoid canal 

 system and the colossal longitudinal oxea of the dermal cortex.. 

 Since then other species which combine these characters have 

 been described, and, although recent authors have not seen fit to 

 accept this genus, we feel that these species form a very natural 

 group, and we consider that the characters distinguishing it are' 

 sufficiently well defined to render it possible to separate it from 

 its nearest ally, Le\ica'ud.ra. In fact, almost the only species that 

 presents any difficulty is Haeckel's Leucandra craonbessa and its 

 varieties, in which the colossal oxea are not arranged longi- 

 tudinally, but lie scattered quite irregularly over the surface of 

 the sponge. This condition is somewhat intermediate between 

 that of some Leucandras and that of Ajyhroceras, and we prefer 

 to place this species in the genus Leucandra. 



It may be advisable to state that we do not consider Aphroceras 

 to have been derived from Ute or a Ute-like form, but directly 

 from an ancesti-al Leucandra. 



We recognise the following species as belonging to this 

 genus : — 



