196 DESCRIPTION OF [Polygastrica. 



Both change of place, and a circulating or oscillating 

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

 l-120th. 



200. EUASTRUM apiculatum. The spinous Euastrum is 

 lenticular and spinous. Size 1- 140th. 



201. EUASTRUM crux melitensis 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 l-570th to l-1150th. 



202. EUASTRUM pecten. The comb-like Euastrum some- 

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

 plate has five obtuse and emarginate lobes. Size 1-1 50th. 



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 1 -280th. 



204. EUASTRUM ansatum. The pivot-like Euastrum, 

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

 somewhat fusiform ; the surface is smooth. Size 1-43 Oth. 



205. EUASTRUM margaritiferum. The pearl Euastrum 

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

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



206. EUASTRUM botrytis. The berry-like Euastrum is 

 figured as augulosum by Ehrenberg. It resembles E. 

 ansatum, but the surface is granulated. Size 1-5 76th. 



207. EUASTRUM integerrimum is a binary elliptical body, 

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

 1 -600th. 



Genus LIV. MICROTHECA. The spinous-disc Animal- 



