768 PROF. A. BENDY AND MR. R. W. H. ROW ON 



the cliiactines as fundamentally rUffei'eut from other subgastral 

 sagittal radiates. 



Megapogon villosus, with its sylleibid canal system and almost 

 syconoid skeleton, exhibits a very interesting stage in the 

 evolution of the leuconoid type, and the same is perhaps true 

 of M. pollicaris. 



We place the following species in this genus :■ — ■ 



1. M. CRISPAXUS Je?i^m. 



Megapogon Gris2)atus Jenkin [1908 B]. 



2. M. CRUCiFERUS PoUjaeff. Type species of the genus. 



Leuconia crucifera Pol ejaefT [1883]. 



3. M. POLiiiCARis Jenkin. 



Megapogon pollicaris Jenkin [1908 B]. 



4. M . RARiPiLUS Jenkin. 



Megapogon raripilus Jenkin [1908 B]. 



5. M. VILLOSUS Jenkin. 



Megapogon villosus Jenkin [1908 B]. 



Genus 35-. Leucandra Haeckel [1872] (emend.). 



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

 persons in which the component individuals are readily 

 recognisable. Canal system leuconoid. Skeleton of the 

 chamber layer more or less confused, but frequently with 

 vestiges of an articulate tubar skeleton in the form of sub- 

 gastral or other sagittal triradiates. Dermal skeleton of 

 tangentially placed triradiates, which may sometimes develop 

 an apical ray. Colossal longitudinally placed oxea, when 

 occurring in the dermal cortex, never forming a smooth 

 layer, but always projecting conspicuously from the surface. 



For illustrations of this genus see Vosmaer [1880] and Dendy 

 [1893 A]. 



The genus Leucandra as here defined is much more narrowly 

 circumscribed than it was by Dendy previously [1892 B]. In 

 fact Dendy's genus is here represented by no less than 10 genera, 

 namely, Leucandra, Baeria, Leucopsila, Aphroceras, Leucettaga, 

 Lamontia and Eilhardia in the family Grantiidfe, and Leuco- 

 malthe, Pericharax and LeuceUiLsa in other families, while 

 certain species have been transferred to Leticetta. On the other 

 hand, we include in the pi^esent genus certain species which 

 possess subdermal quadriradiates, and which on that account 

 were placed by Dendy in the genus Leucilla ; for, as we had 

 occasion to point out with regard to both Leucetia and Grantia, 



