ACHNANTHES. 279 



I. Valve with costce, between which are two rows of small beads. 



A. longipes C. Ag. (Syst., p. I ; Consp., p. 58, No. 1 ; H.V.H. 

 AtL, pi. 26, f. 13, 14, 15, and 16*; Type No. 229), plate 8, fig. 323. 



Valves linear-elliptic, constricted at the median portion, with apices more 

 or less obtuse, furnished with strong transverse costaj, about 6 in 1 c.d.m., 

 between which are two rows of beads, sometimes opposite, sometimes alter- 

 nate ; upper valve without raphe, having sometimes at the apex a small hyaline 

 area (Grunow) ; lower valve with a raphe surrounded by a feeble hyaline zone. 

 Central nodule dilated transversely into a narrow stauros. Frustule with 

 connecting zone finely striated transversely, the striae interrupted by longi- 

 tudinal plaits. Length, about 5 to t8 c.d.m. 



Marine. Ostend. England (Kitton, Comber, Stolt, Norman), Ireland (O'Meara), Denmark, 

 Norway. 



II. Valve beaded, without costw. 



*Lower valve with a stauros. 



a. UPPER VALVE WITH RAPHE CENTRIC, FLEXED, 



A. brevipes C. Ag. (Syst, p. i, Consp., p. 59, No. 3; H.V.H. 

 AtL, pi. 26, f. 10, n and 12* ; Type No. 227), plate 8, fig. 324. 



Valves linear-lanceolate, median portion constricted, apices cuneate ; striae 

 about 7 in 1 c.d.m., composed of 2 to 7 coarse beads ; upper valve without 

 raphe, lower valve with raphe surrounded by a distinct hyaline area, increasing 

 in breadth towards the median portion. Central nodule dilated into a rather 

 broad stauros. Connecting zone as in the preceding. Length, 7 to 10 

 c.d.m. 



Marine. Ostend. England (Kitton, Comber, Stott, Norman). Scotland. Ireland (O'Meara). 

 Probably on all the shores of the North Sea. 



A. subsessilis Ehr. (inf., p. 228, pi. 20, f. 3; h.v.h. AtL, pi. 



26, f. 21, 22, 23 and 24* ; Type No. 231), plate 8, fig. 325. 



Differs from the preceding, with which it is connected by intermediate 

 forms, by the obtuse-rounded apex of the valves, its smaller size and its 

 finer striae, about 10 in 1 c.d.m., formed of 4 to 7 beads. Length, 3 to 5 

 c.d.m. 



Marine. Antwerp, Ostend. Holland (H.V.H.). England (Kitton, Comber, Stolt, Norman). 

 Scotland. Ireland (O'Meara). Probably throughout the North Sea. 



