194 DESCRIPTION OF [Polygastrica. 



lorica is rough. Found, with other Bacillaria, in slime 

 amongst conferva and oscillatoria. Size of star 1-1 150th 

 to l-210th. 



195. MICRASTERIAS angulosa has fifteen to sixteen 

 bodies, arranged in a double series around a single one. 

 The edges are truncated. Found with the preceding. 

 Size l-430th to l-280th. 



196. MICRASTERIAS rotula. The wheel-like Micras- 

 terias varies in its mode of arrangement ; it has usually 

 eleven in the outer series, five in the second series, and 

 one in the centre ; they are often elongated and rayed, 

 and the margins variously excised. Colour a superb yel- 

 lowish-green. Diameter of star 1 -800th to 1 -400th. 



(***) Cirlce triple. 



197. MICRASTERIAS tricyclia has three series of bodies ; 

 fifteen are in the first or external one, eight or ten in the 

 second, and four or five in the third or most internal one. 

 The margins are variously excised. Found amongst 

 floccose conferva. Diameter of star l-720th to l-210th. 



(****) Circles more than three. 



198. MICRASTERIAS elliptica. The elongated Micras- 

 terias has four series of bodies, usually twenty-three in the 

 outer one, and two in the middle. Found with the pre- 

 ceding. Size of star l-280th to l-210th. 



Genus LIII. EUASTRUM. The star-disked Animalcules 

 are distinguished by their members being free, inclosed in 

 a simple compressed lorica, composed of only one piece, 

 and by their adhering in pairs, which are disposed in the 



