CALCAREOUS SPONGES. 743 



Genus 15. Sycetta Haeckel [1872] (emend.). 



JDiagnosis. The radially arranged flagellate chambers always 

 completely separate from one another, and never possessing 

 tufts of oxea at their distal ends. With no properly defined 

 inhalant canals leading to the prosopyles. 



For illustrations of this genus see Haeckel [1872] under 

 Sycaltis conifera and Sycetta primitiva. 



This is the simplest of all the genera with syconoid canal 

 system, its primitive nature being shown by the absence of fusion 

 between the flagellate chambers and by the absence of tufts 

 of oxea at their distal ends, unless, indeed, this absence is due to 

 the disappearance of ancestral oxea. 



Sycetta asconoides Breitfuss [1896 B], to judge by the published 

 description, apparently occupies an intermediate position between 

 Sycetta and Sycon, as these genera are understood by us. The 

 description states that the flagellate chambers are fused together 

 laterally, but that they have no tufts of oxea at their distal ends. 

 During a recent visit to Berlin, however, one of us (Row) had 

 the opportunity of examining one of the type slides Of this 

 species, and found that Breitfuss had overlooked the presence of 

 a few tangentially placed dermal triradiates. The occurrence of 

 these spicules, of course, places the species in the genus Grantia in 

 the family Grantiidae, of which it is one of the simplest forms. 



We include the following species in this genus : — 



1. S. CONIFERA Haeckel. 



Sycaltis conifera Haeckel [1872]. 



2. S. PRIMITIVA Haeckel. Type species of the genus 



Sycetta p7-imitiva Haeckel [1872]. 



3. S. SAGiTTiFERA Haeckel. 



Sycetta sagittifera Haeckel [1872]. 



Genus 16. Sycon Risso [1826] (emend.). 



Diagnosis. Radial chambers usually more or less united at places 

 where they come into contact with one another, and always 

 crowned distally with tufts of oxeote spicules. Properly 

 defined inhalant canals usually present, the outer ends of 

 which may be covered by a thin pore-bearing dermal 

 membrane without special skeleton. 



For illusti-ations of the structure of this genus see Schulze 

 [1875] and Dendy [1893 A]. 



As pointed out by Dendy [1893 A] the most characteristic 

 feature of this genus is aflforded by the tufts of oxeote spicules 

 which crown the distal ends of the radial chambers, taken in 



