446 



CYCLOTELLA. 



ANALYSIS OF SPECIES. 



Valve with margin strongly striate, with centre coarsely punctate and 



usually near the margin of the latter a demi-circle of coarse puncta . C. striata. 



f Valve having in the central portion a rosette of elevated triangu- 

 lar dots . . . . . . C. antiqua. 



o 



a 



o 



a 



a 

 > 



I 



Valves 



without 



elevated 



triangular 



dots. 



f Marginal stria; intermixed with much stronger 



striae, at regular distances . . . C. comta. 



L 



Marginal striae intermixed with small 



All the 



striae 

 equally 



well 

 marked. 



spines 



Striae 

 without 



small 

 spines. 



C. operculata. 



f Marginal striae very ro- 

 bust ; puncta radiant . 



j Marginal striae feeble ; 



"i centre with fine scat- 

 tered puncta some- 

 times mixed with some 



C. Meneghiniana. 



coarse dots 



C. Kutzingiana. 



C. Striata (Kiitz.) Grun. (Coscinodiscus striates Kutz.; Cydotelia 

 Daliasiana W.Sm. ; H.V.H. Atl., pi. 92, f. 6-10* ; in Type No. 320; var. 

 stylorum, Type No. 474), plate 22, fig. 651. 



Valve with margin strongly striate, centre coarsely punctate, puncta 

 scattered. Centre often bordered with a semi-circle of more distant puncta ; 

 7 to 12 costae in 1 c.d.m. at the margin of the valves. Diameter, 3 to 8 

 c.d.m. 



Marine. Antwerp (Scheldt, H.V.H. ), England (Dallas, Kitton, Norman). 



C. antiqua W. Sm. (S.B.D., i., p. 28, pi. 5, f. 49; H.V.H. Atl., 

 pi. 92, f. 1*), plate 22, fig. 652. 



Valves with well-marked marginal costae, intermixed with spines or coarse 

 dots, centre finely granular, with 6 to 15 triangular elevations. Diameter, 1*5 

 to 3 c.d.m. 



Fresh water. Not yet found in Belgium. England (Norman) ; Western Islands (Baxter Coll., 

 Nos. 2733, 2734) ; Peterhead Deposit (Baxter Coll., No. 2737); Aberdeen Deposit (T. and P., No. 

 443) ; Ireland (W. Sm.) ; Norway, Finmark, &c. 



C. COmta (Ehr.) Kutz. (Spec. Alg., p. 20 ; Discoplaa comta Ehr. ; 

 H.V.H. Atl., pi. 92, f. 16-22* j in Type No. 424), plate 22, fig. 653. 



Valve with well-marked marginal costae, each third or fourth costae being 

 much more vigorous than the others ; central portion finely striate, striae 

 punctate or more or less radiant. Girdle face somewhat inflated in the 

 middle. Frustule plane, not undulated. Diameter, 75 to 3 c.d.m. 



Fresh water. Antwerp (H.V.H.), England (Kitton). 



