STUDIES ON THE COMPARATIVE ANATOMY OF SPONGES. 239 



series of variations as in the Grantidsej and the shape and 

 arrangement of the chambers, as in that family^ can only be 

 utilised as an aid in diagnosing the genera. 



The family is evidently derived from an ancestral Grantia- 

 like type, as is clearly indicated by the retention of the primi- 

 tive radial arrangement of the chambers, and the articulate 

 tubar skeleton, by the least modified species (fig. 18). 



The family^ as here maintained, is not nearly identical with 

 any which have hitherto been proposed. No previous writers 

 have drawn that sharp distinction between subdermal sagittal 

 triradiates and subdermal quadriradiates which I have indi- 

 cated in dealing with the skeleton, and which seems to me to 

 be of the greatest value for purposes of classification. 



I have adopted the name " Heteropidse," not because I 

 regard the genus Heteropia as most typical of the family, 

 but because a family name derived from the principal genus, 

 Grantessa, would be liable to confusion with the name 

 " Grantidse/^ already used for the preceding family. 



Genus 13. — Grantessa (von Lendenfeld [11], emend.), 



fig. 18. 



Diagnosis. — The flagellated chambers are elongated, and 

 arranged radially around the central gastral cavity. The 

 dermal cortex consists principally of triradiates, and does not 

 contain longitudinally disposed oxea. 



Remarks. — In working over the Australian Heterocoela I 

 met with an extensive series of specimens, belonging to at least 

 six species,! which evidently formed a very natural assemblage, 

 characterised by essentially the same peculiarities of skeleton 

 and canal system. Most of these species had already been 

 described by various authors under a variety of generic names, 

 viz. Amphoriscus(PolejaeflP), Grantessa (von Lendenfeld), 

 Heteropia (Carter), Hypograntia (Carter), and Leuconia 

 (Carter). 



From these names I selected Grantessa for the group of 

 species in question, for the following reasons : — The name Ara- 

 ' For a list of these species, with synonyms, vide 4. 



VOL. 35, PART 2. — NEW SEE. S 



