STUDIES ON THE COMPAEATIVE ANATOMY OF SPONGES. 231 



of the chambers. I have already given my reasons for coming 

 to this conclusion in discussing the canal system. 



Family 3. — Grantid^, Dendy (4). 



Diagnosis, — There is a distinct and continuous dermal 

 cortex, completely covering over the chamber layer, and pierced 

 by inhalant pores. There are no subdermal sagittal triradiates, 

 nor conspicuous subdermal quadriradiates. The flagellated 

 chambers vary from elongated and radially arranged to 

 spherical and irregularly scattered ones^ while the skeleton of 

 the chamber layer varies from regularly articulate to irregu- 

 larly scattered. 



Remarks. — This family does not nearly correspond with 

 any which has hitherto been proposed ; for, disregarding 

 differences in canal system, I include therein some genera 

 with a Syconoid and others with a Leuconoid type, and rely 

 upon the structure of the skeleton for thus uniting them. I 

 believe myself to be justified in this course of action by the 

 great variation of the canal system which has been shown to 

 exist in closely related forms and even in the same species, 

 and which I have already discussed in a previous part of this 

 paper. 



The family, as here constituted, is distinguished from the 

 Sycettidse by the positive character afforded by the develop- 

 ment of a strong dermal cortex, and from the Heteropidse and 

 Amphoriscidse by the negative characters afforded by the 

 absence of subdermal triradiates or quadriradiates. It is 

 very difficult to diagnose the family, which is a very compre- 

 hensive one, so as to exclude the Leucascidae, but the latter 

 present a peculiar combination of skeleton and canal system 

 which is not to be found amongst the Grantidse, and appear 

 never to have passed, as I believe all the Grantidae have, 

 through a primitive Syconoid stage with radially symmetrical 

 skeleton. 



Genus 5. — Grantia (Fleming, emend.), figs. 9, 10. 

 Diagnosis. — The elongated flagellated chambers are ar- 



