148 DESCRIPTION OF [Pohjyastrica. 



glands dispersed, or placed in a number of series; rays 

 obscure. Found among oscillatoria. Length l-140th to 

 l-60th. 



109. Closterium digitus. The finger-shaped CIos- 

 terium. — Lorica smooth, straight, ovato-C5dindrical, four 

 times as long as broad, and considerably rounded at the 

 ends. Traces sometimes of a triple self- division, and 

 longitudinal fillets undulating along the edges. Found 

 amongst conferva. Length 1 -240th to l-120th. 



110. Closterium attenuatum. The slender -formed 

 Closterium. — Lorica smooth, crescented, or slightly curved, 

 and tapering considerably towards the extremities, which 

 are obtuse ; glands in a single series along the middle, 

 with no central transverse rays. Length l-48th. 



111. Closterium cornu. The horn-shaped Closterium. 

 — Lorica smooth, very slender, slightly curved, and ap- 

 proaching to cylindrical, with the apices truncated. Fillets 

 green, undulating. Found amongst conferva. Length 

 1- 900th to 1-1 20th. 



112. Closterium? cylindrus. The cylinder -shaped 

 Closterium. — Lorica ovato-cylindrical ; scarcely three times 

 as long as broad, shghtly constricted at the middle, and 

 very obtuse at both extremities. Marked exteriorly with 

 granulated radiations of the shell. Length l-4.30th. 



113. Closterium margaritaceum. The pearly Clos- 

 terium. — Lorica straight, cylindrical, and elongated, eight 

 or nine times as long as broad, and slightly constricted at 

 the middle, rounded at both extremities, and marked 

 exteriorly with strings of pearl-like granules ; moveable 

 points at some distance from the extremity. Length 

 1 -240th to I -200th. 



