432 



SYNDETOCYSTIS. 



GENUS 100. SYNDETOCYSTIS RALFS. Manuscr., 



1864. 



Valves subcircular, with dentate 

 margins ; having in the centre a cylin- 

 drical process, curved into a hook, 

 which unites the valves to that of the 

 next frustule, and thus produces a 

 filament. 



We reproduce (fig. 155), after Walker 

 and Chase, Syridetocystis Barbadensis Ralfs, 

 a very curious form, found in the Cam- 

 bridge Estate Deposit, Barbadoes. 



In the Manuscript for the Fifth 

 Edition of Pritchard, which forms part of 

 my library, Ralfs thus expresses himself : 

 " Syndetocystis N. G. Ralfs. Frustules 

 as in Biddulphia, but connected in a 

 chain-like manner by strong spines from 

 the centre of their valves. The frustules 

 in the front view resemble those of the 

 p. other genera of this family, except in 



Syndocystis Barbadensis. having from the centre of each valve a 



stout central spine, which is suddenly bent near the end and curved in a link- 

 like manner round a similar spine from the adjacent frustule. In the fossil 

 state at least these spines slide upon each other, altering the distance between 

 the frustules, as is well shown in fig. 155, taken from a very perfect specimen 

 belonging to our friend Mr. Norman, of Hull. 



" S. Barbadensis Ralfn., also from Cambridge Deposit, Barbadoes. Mr. 

 Johnston. 



" Valves broadly elliptical or suborbicular, with a process near each apex 

 and one or more subulate spines, which are best seen in the front view. Sur- 

 rounding the stout central spine is a large smooth portion, bordered by a 

 circlet of pearly granules, from which radiate rows of granules." 



