618 DE8CEIPTI0N OF {Tolygontrica. 



portion attenuated, looking as if shortly homed. Diameter l-576th. 

 Found in the Baltic. 



Peeidnidm macroceros. — ^Yellow; habit of P. tripos, hut more 

 slender, and A^ith longer horns, which are four times the length 

 of the body. Length 1 -216th. In the Baltic Sea. 



P. monas. — Very«mall, oblong, obtuse, without horns, remarkably 

 social. Diameter 1-1 728th. In the Baltic. 



P. Tridens. — Yellow, with the habit of P. favum, P. divergem, and 

 of P. Michaelis ; surface granular, with three acute frontal horns ; 

 and its posterior portion attenuate. Size l-576th. In the Baltic. 



Genus Glenodintum. The tvreath Animalcules, with eyes. — Peri- 

 dina3a with mobile cilia, placed in a transverse furrow, or zone, and 

 provided with an eye. The organization is much the same, in other 

 respects, as in the precediag genus. In G. cinctum only is a fiHfonn 

 proboscis seen ; this emanates from the middle, and, like the wi'eath 

 of cilia vibrates. This organ, though hitherto unobserved, is pro- 

 bably present in the other species. The lorica is combustible. The 

 stomach-cells, and minutely-granulated ova are visible in all the 

 species, but the foi-mer are very distiact in G. apiculatum. The red 

 eye is in the foiTii of an elongated or horse-shoe shaped spot, and forms 

 an essential character of the genus. Longitudinal self-division has 

 been observed only in G. cinctum. 



G. cinctum = Peridinium oculatum (Duj.) — Lorica oval, or nearly 

 spherical and smooth ; eye large, semi-lunar, and transverse. Found 

 in fi'esh water, amongst Oscillatoria. Size 1-5 70th. 



G. tahulatum. — Is oval, of a yellowish-green colour ; lorica granu- 

 lar and reticulate with elevated lines, but not spinous ; tnmcate 

 and denticulate posteriorly, and bidentate anteriorly ; eye oblong. 

 Size 1 -570th. to 1 -430th. 



G. apiculatum. — Is oval, of a yellovrish green colour ; lorica smooth, 

 but with hispid fuiTows on the margin, as shewTi in figs. 224, 225, 

 and 226. The eye is oblong, and extremities obtuse. Found amongst 

 Conferva, where Chara grows. Size l-570th. to l-430th. 



