JOHNSTON, O.N D1ATOMACE2E. 13 



Of this and the following elegant species I have met with 

 but a single example, although I have searched diligently in 

 numerous preparations. 



In the specimen above noticed the canaliculi numbered 

 thirty- seven. 



C. marginatus, n. sp. — Disc ovoid, bent; rays numerous, 

 marginal, short, separated externally by a nodule, and in- 

 ternally also by a larger one on either side of the trans- 

 verse axis ; the inclosed field divided by a longitudinal 

 fusiform of smooth space; the remainder marked by rows 

 faint dots, straight in the direction of the transverse axis, 

 but becoming concentric with the extremities of the long 

 axis. Diameter sis"' (Fig- 11.) 



In Elide guano. 



Cocconeis, Ehr. 



C. regina, n .sp., C. J. — Frustule ovoid, bluish green ; 

 striae numerous, 20 in 0-001", concentric around the extre- 

 mities; on either side of the nucleal line the extremities 

 of the striae distinctly granular ; in their course outwards 

 faintly moniliform, but more conspicuously beaded periphe- 

 rally, forming a sort of margin of the width of three or four 

 granules. Diameter x\m". (Fig. 12.) 



In Elide guano. 



This exquisite species is not abundant in the residue fur- 

 nished by the guano. There is but little variation in size, 

 the diameter given above being that of the largest frustule 1 

 have encountered. 



Stauroneis, Ehr. 



S. angulata, n. sp. — General form of the valve elon- 

 gated oval, extremities somewhat acuminate; the marginal 

 line bending on either side as it advances at about one third 

 the distance from the transverse axis, at which it makes a 

 wide but distinct angle. A narrow band of finely granular 

 striae, disposed transversely, surrounds a clear field, and, 

 becoming suddenly narrower at the extremities, is continuous 

 on either side of the carina with a delicate longitudinal band 

 of very minute granules, terminating in a point outwardly 

 at the stauros, which is short. Edge beaded. Diameters 



1 HI w 1 III 



275 X J ±2 • 



In Elide guano. 



Heliopelta, Ehr. 



H. Phaeton, n. sp. — Frustule quasi-orbicular, many 

 sided, the number of sides being twice that of the rays. 



