244 DESCRIPTION OF [Polygastrica. 



FAMILY XII. PERIDINAEA 



Comprehends vibrating animalcules, distinctly or appa- 

 rently polygastric, devoid of an alimentary canal, covered 

 with a shell, or lorica, upon which, or upon the body, are 

 cilia or setae : these are often arranged in the form of a 

 girdle or crown hence the name is derived. The lorica 

 has only one opening. In three out of the four genera 

 an organ of locomotion is present, in the form of a delicate 

 proboscis, independent of the wreath of cilii around the 

 middle of the body, or scattered cilii, or bristles. In 

 Peridinium pulvisculus and cinctum only has artificial 

 means succeeded in demonstrating the nutritive appa- 

 ratus ; for it is mostly covered by clusters of ova. In 

 Peridinium tripos the seminal glands are evident. In 

 four species, a system of sensation is indicated by the 

 presence of a red-coloured visual point. 



The genera are disposed as follows : 



Lorica having stiff bristles or short spines- ( no e y e Chaetotyphla. 



no transverse furrowed zone { ey e present .. Chaetoglena. 



Lorica smooth or rough-a ciliated transverse f no e y e " ' ' Peridinium. 



zone present ( eye present .... Glenodinium. 



Some of the species have been found only in a fossil 

 state ; these are obtained from the chalk formations in 

 flint, but are not figured in Die Infasionsthierchen. 



Genus LXXXIII. CHAETOTYPHLA. The bur Animal- 

 cules have a siliceous lorica, hispid or spinous, destitute 

 of a transverse furrow or zone, and visual organ. The 



