Peridinaea.] THE INFUSORIA. 245 



surface is covered with little spines and bristles, which 

 appear stronger at the posterior portion of the body. By- 

 pressing the animalcule between the plates of an aquatic 

 live-box, the lorica bursts, and sets the little creature in 

 the interior of it at liberty. In swimming it revolves 

 upon the longitudinal axis ; this is probably produced by 

 a delicate filiform proboscis or cilii, at its mouth ; but 

 though this motion is evident, the organs producing it 

 have not been discovered. Of the nutritive, sensitive sys- 

 tems, &c., nothing positive is known. One species has 

 been discovered in flint, which so closely resembles 

 Zanthidium, that it is often mistaken for it. 



366. Chaetotyphla armata. The spinous Chaeio- 

 typhla is of a brown colour, ellipsoidal form, with rounded 

 ends ; the posterior is covered with short spines, and has 

 a circlet of black spots, as shewn in the end view, fig. 215. 

 The anterior cilii, or fine bristles, are sometimes very 

 indistinct. Figure 214 is a variety in which they are 

 strongly marked. Found in clear water, amongst conferva. 

 Length l-620th. 



367. Chaetotyphla aspera. The rough Chaetotyphla 

 is brown, has an oblong body, rounded at both ends, and 

 rough, with short bristles ; the little spines are scattered 

 without order at the posterior end. Found with the pre- 

 ceding. Length l-570th. 



368. Chaetotyphla (?) pyritae. The flint Chaetotyphla 

 has an oblong cylindrical body, rounded at both ends, and 

 provided with delicate elongated bristles, but destitute 

 of spines. Found, fossil, in flint, near Delitzsch. Size 

 1-1 150th. 



Genus LXXXIV. Chaetoglena. The bristled and 



