196 ARTHUR DENDY. 



The development of the dermal skeleton varies much in 

 different species as regards its extent, but always follows the 

 same pattern. The large longitudinally arranged oxea always 

 form the most conspicuous feature, and frequently give to the 

 surface of the sponge a very characteristic striated appearance. 

 Nearly always, however, triradiates and minute surface oxea 

 are also present, arranged asinGrantia. InUtespiculosa 

 and U. Spenceri (4) the triradiates are very numerous 

 indeed, while in U. glabra (5), U. argentea, and U. 

 syconoides (4) they are very scarce. 



The presence of the longitudinally disposed oxeote spicules 

 in the dermal cortex, although often giving the sponge a very 

 characteristic appearance, is by no means peculiar to the genus 

 Ute, for the same character is found in Leucandra alci- 

 cornis (5) and in two species of Homocoela Simplicia, viz. 

 Leucosolenia asconoides (4, 12) and L. uteoides (16); 

 and it is also characteristic of the genus Heteropia (4). 



In Ute spiculosa (4), where the mesoderm is very strongly 

 developed, we find, in accordance with the rule laid down 

 above, that the skeleton of the chamber layer is dense and 

 irregular, though showing traces of the normal articulate 

 arrangement in the usually centrifugal direction of the basal 

 rays of the triradiates. 



In Ute Spenceri (4) we find one or two slight pecu- 

 liarities in the skeleton. Thus we find, as in Grantia 

 labyrinthica, a number of minute oxeote spicules on the 

 . gastral as well as on the dermal surface; and we find also that 

 the exhalant canals are protected by quadriradiates of special 

 form. The tubar skeleton is distinctly articulate, though 

 becoming confused as it approaches the dermal cortex. 



Synute (fig. 15). 

 In this sub-genus the dermal cortex and its contained 

 spicules are enormously developed, so as to bind together all 

 the individuals of a branching colony into one continuous 

 whole (fig. 15). Here, as in other cases where the dermal 

 cortex is very strongly developed, the cortical triradiates lose 



