AMPHORA. 129 



Frustule almost rectangular, three times longer than broad. Valve linear 

 with apices broad, unilaterally rounded. Raphe gently bi-arcuate, distant 

 from ventral side. Axial area indistinct on dorsal side. Central area absent 

 or orbicular. Striae of dorsal side 10 to 14 in 1 c.d.m., coarsely punctate, not 

 interrupted, with indistinct longitudinal line. Ventral side broad, with striae 

 radiant, coarsely punctate, sometimes crossed by a narrow hyaline band. 

 Length of frustule, 4 to 7 c.d.m. Breadth, 17 to 2-1 c.d.m. Breadth of 

 valve, 1 c.d.m. 



Marine. Coasts of Belgium and England (Cleve). 



Var. major A. Baltic Sea (CI). 



A. marina H. Van Heurck (h.v.h. Atl., pi. i, f. 16*; 



in Types Nos. 101 and 517), plate 1, fig. 14. 



Frustule oblong, very inflated at median part, infinitesimally attenuated as 

 far as the apices which are truncate. Valves with dorsal margin very convex, 

 and ventral margin slightly and almost regularly concave ; raphe well marked, 

 inflexed at median part ; striae rather strongly punctated on dorsal side ; 

 about 16 in 1 c.d.m., same number at ventral margin. Length, 4 to 5 c.d.m. 



Marine. Shores of North Sea: England (W. Sm.), France (Grun. , Brdb.), Belgium: Scheldt. 

 (H. Van Hk. ), and probably on all shores of North Sea. 



According to Prof. Cleve this form should be recorded as having been 

 first described by me, and the A. marina of Wm. Smith treated as only a form 

 of A. Proteus. 



A. robusta Greg. (Diat. of Clyde, p. 44, pi. 5, f. 79; Ad. S. 

 Atl, pi. 27, f. 40-41*); plate 24, f. 670. 



Frustule broadly oval with truncate or sub-truncate apices. Valve arcuate, 

 with apices obtuse, raphe very inflexed, central nodule large, surrounded by a 

 blank space slightly stauroform. Ventral margin concave. Ventral part of 

 valve completely striated, striae with coarse puncta, 7 to 8 in 1 c.d.m. Sutural 

 zone completely smooth. Length, 8 to n c.d.m. 



Marine, Scotland (Gregory) and Shores of North Sea; Belgium: Scheldt (H. Van Hk.) 



A. Proteus Greg. (Diat. of Clyde, p. 46, pi. 5, f. 81; Ad. Sch. 

 Atl., pi. 27, f. 2-3; 5-6*); plate 24, fig. 671. 



Frustule elliptic, with truncate apices. Valve with dorsal margin arcuate, 

 ventral margin concave, apices obtuse. Raphe very inflexed ; central nodule 



K 



