1908.] 



AFRICAN CALCAREOUS SPONGES. 



445 



Canal-system. — There ai-e large incurrent chambers under the 

 dermis from which the large incurrent canals run radially 

 inwards. The excurrent canals are also large and run radiall}'- 

 between the others ; they communicate with the gastral cavity 

 through large ports. 



Zieucandra ananas, spicules. X 56. 

 (For explanation of the letters see text below.) 



Skeleton. — The dermal skeleton consists of a thin layer of 

 delicate triradiates lying without orientation . Tufts of large 

 oxea project radially from slightly raised papilla? on the dermis. 

 The body skeleton consists of irregularly placed large triradiates. 

 The excurrent canals are lined with quadriradiates, the apical 

 rays projecting into the canals. The gastral skeleton consists 

 of a dense layer of quadriradiates with the apical rays projecting 

 into the gastral cavity. 



The specimen agrees fairly well with Haeckel's description of 

 Leucandra ananas, though the spicules are rather larger, and the 

 dermal skeleton difiers from the body skeleton, which is not men- 

 tioned by Haeckel. Haeckel, however, makes a similar omission 

 in other cases, e. g. in his description of Leucandra fistulosa. 



Sjyicules (text-fig. 92). 



The oxea are of one sort- : — 



(«) Nearly sti-aight sharply-pointed oxea, 700-3000 fx long x 

 28-46 fx thick. 



