744 PROF. A. BENDY AND MR. R. W. H. ROW ON 



conjunction with the absence of a dermal cortical, as distinct 

 from a tubar, skeleton. In the more specialised species a pore- 

 bearing dermal membrane stretches between the distal ends of the 

 radial chambers, covering over the ends of the inhalant canals, but 

 this contains no special skeleton of its own. The flagellate 

 chambers may also exhibit a considerable amount of branching 

 towards their distal extremities, but they never lose their 

 elongated character and i-adial arrangement. 



The genus is sharply distinguished from Sycetta by the presence 

 of the tufts of oxea at the distal ends of the chambers, less 

 sharply from Grantia by the absence of a special dermal cortical 

 skeleton. 



We include in our conception of the genus Sycon von. 

 Lendenf eld's genera Homoderma and Sycantha, and Jenkin's. 

 Tenthrenodes antarcticus, Sireptoconus av,strcdis and Hy])odictyon 

 longstaffi. We have ah-eady mentioned that Ho'taoderma is. 

 merely a Sycon with persistent collared cells in the central 

 gastral cavity. Jenkin [1908 B] has .shown conclusively that 

 Sycantha tenella is a typical Sycon, but has erected a new genus 

 Tenthrenodes for " Sycettidse with linked chambers," an almost 

 identical character with that on which the genus Sycantha was 

 founded; and although Dendy [1893 A] retained Sycantha on 

 these grounds, we no longer consider that such "linking" can be 

 regarded as of generic importance. We may point out here that 

 Tenthrenodes scotti, the other species included by Jenkin in his 

 genus, is placed by us in the genus Grantia, on account of the 

 presence of tangential triradiates in the dermal cortex. Strepto- 

 conus aiostralis and Hypodictyon Zowg's^a;^ are " chiact" -bearing 

 forms which were placed by Jenkin in his family Chiphoridje. 



We assign the following species to the genus : — 



1. S. ALOPECURUS Haeclcel. 



Sycum alopeciortis Haeckel [1870]. 



Syca.nd,ra ampulla var. alopecurus Haeckel [1872]. 



2. S. AMPULLA Haeckel. 



Sycarivm ampulla Haeckel [1870]. 

 Sycon petiolatus 0. tSchmidt MS.,j^fZ6 Haeckel [1872]. 

 Sycum petiolat%im Haeckel [1870],^c?e Haeckel [1872]. 

 Sycandra ampulla Haeckel [1872]. 



3. S. ANTARCTicuM Jenkin. 



Tenthrenodes antarcticus Jenkin [1908 B]. 



4. S. ARCTicuM Haeckel. 



Sycum arcticum Haeckel [1870]. 



Sycon ra'phanus 0. Schmidt [1870],j^fZe Haeckel [1872].. 

 Sycandra arctica Haeckel [1872]. 



5. S. ASPERUM Gibson. 



Sycandra aspera Gibson [1886]. 



