196 DESCRIPTION OF [Polygastrica. 



Both change of place, and a circulating or oscillating 

 motion, have been noticed. Size of disc l-280th to 

 l-120tb. 



200. EuASTRUM apiculatum. The spinous Euastrum is 

 lenticular and spinous. Size 1- 140th. 



201. Euastrum cn/.r me/i/ewm is lenticular and smooth, 

 the margin is deeply indented, giving them the form of a 

 Maltese cross, as seen at fig. 124. Their locomotion is 

 periodical, and very difficult to be seen ; old specimens 

 have as many as forty marginal teeth, young ones only 

 twelve. Size 1-5 70th to 1-1 150th. 



202. Euastrum ^ec^ew. The comb -like Euastrum some- 

 what resembles the next species, but is smooth, and each 

 plate has five obtuse and emarginate lobes. Size l-150th. 



203. Euastrum verrucosum is shewn at fig. 125 ; the 

 surface is rough and tuberculated. Ehrenberg's observa- 

 tions were made on green specimens, but Corda represents 

 the contents of the body as brown. Size l-280th. 



204. Euastrum ansatum. The plvot-like Euastrum, 

 when young, is oval, but when full-grown the pair becomes 

 somewhat fusiform ; the surface is smooth. Size l-430th. 



205. Euastrum margaritiferum. The pearl Euastrum 

 is curiously granulated. (See fig. 126.) Spontaneous 

 motion has been observed. Size 1- 1440th to 1- 280th. 



206. Euastrum botrytis. The berry-like Euastrum is 

 figured as augulosum by Ehrenberg. It resembles E. 

 ansatum, but the surface is granulated. Size 1 -576th. 



207. Euastrum integerrimum is a binary elliptical body, 

 with the surface and margin smooth. Size 1 -480th to 

 1- 600th. 



Genus LIY. Microtheca. The spinous-disc Animal- 



