CALCAREOUS SPONGES. 729 



Genvis 3. Ascute nov. 



Diagnosis. The diverticula of the gastval ca.vity, if aiiy, never 

 radially arranged around a central tube. With a uteoid 

 dei'mal skeleton of colossal longitudinal oxea. Nuclei of the 

 collared cells (? always) basal. 



As the presence of a uteoid dermal skeleton is considered to 

 form a good generic character in other families, we see no reason 

 why it should not be used in the same way amongst the Homo- 

 coelidse, and therefore propose this genus for Dendy's Leucosolenia 

 uteoides, with which Carter's Ajyhroceras asconoides is doubtless to 

 be associated. The nucleus of the collared cells is basal in the 

 former sjtecies, but its position is not known in the latter. 



In both the known species of this genus the sponge has the 

 form of a group of simple ascon persons, attached to one another 

 by their bases, and without any anastomoses in the colony. 



We recognise the following species as belonging to this 

 genus V — 



1. A. ASCONOiBBS Garter. 



Aphroceras asconoides Carter [1885-1886]. 



2. A. UTEOIDES Bendy. Type species of the genus. 



Leucosolenia uteoides Dendy [1892 C]. 



Genus 4. AscYSSA Haeckel [1872]. 



Diagnosis. Diverticula of the gastral cavity, if any, never radially 

 arranged around a central tube. Skeleton consisting entirely 

 of oxea. 



For illustrations of this genus see Haeckel [1872]. 



We consider the entire absence of radiate spicules as affording 

 sufficient reason for the generic separation of Haeckel's two 

 species of Ascyssa from all the other Homocojlidse. 



We assign the following species to this genus: — 



1. A. ACUFERA Haeckel. 



Ascyssa acufera Haeckel [1872]. 



2. A. TROGLODYTES Hacckel. Type species of the genus. 



Ascyssa troglodytes Haeckel [1872]. 



Family 2. LEUCASCID^ Dendy [1892 B] (emend.). 



Diagnosis. Sponge typically forming a massive colony, usually 

 with several or many oscula, but sometimes integrated into 

 a single individual with definite external form. Without 

 any large central gastral cavity lined by collared cells, but 

 with an exhalant canal system devoid of collared cells. 



