130 AMPHORA. 



rather large, often furnished with a stauroform blank space. Ventral part of 



valve having only a few rows of dots. Striae very distinct with robust puncta ; 



8 to 10 in 1 cd.m. Length very variable, from 7 to 15 c.d.m. Breadth, from 



4 to 6 c.d.m. 



Marine. Scotland (Greg.), England, Belgium! Germany! Norway ! etc. 



2. Psammamphora CI. Ventral part rather broad. The two parts 

 finely puncto-striated. Puncta not forming longitudinal lines. (Type 

 form : A. arenaria). 



ANALYSIS OF SPECIES. 



Frustule with outer margins slightly introrlexed, valves furnished with 



a stauros ........ A. ocellata. 



Frustule with outer margins slightly gibbous, valves without stauros . A. arenaria. 



A. OCellata Donk (Q.J.M.S., i86i, p. n, pi. i, f. nb; H.V.H. 

 Atl, pi. 1, f. 26*); plate 1, fig. 3. 



Frustule quadrangular, with rounded apices and outer margins slightly 

 introflexed. Valve with raphe infinitesimally incurved ; striae very fine and 

 very delicate. Length, 6 to 9 c.d.m. 



Marine. Found in washings of mussels and in the residue of a washing of sand from the beach 

 at Blankenberghe. England ; Ireland ; France. 



A. arenaria Donk. (T.M.S., 1853, p. 31, pi. 3, f. 16; Ad. Sch. 

 Atl., pi. 40, f. 8-10*) ; plate 24, fig. 673. 



Frustule hyaline, subquadrangular ; apices rounded, truncate ; median 

 portion often slightly gibbous ; raphe very inflexed. Valve broad, arcuate ; 

 apices very obtuse ; terminal nodules recurved near the outer margin, rather 

 broad and very elongated. Ventral portion of the valve very broad, finely 

 puncto-striate, as is also the dorsal portion. Length, 10 to 12 c.d.m. 



Marine. England (Norman) : Ireland (O'Meara) ; Shores of the North Sea. 



3. Cymbamphora CI. Striae not forming longitudinal lines, and not 

 distinctly beaded. Ventral portion of valve very narrow. (Type 

 form : A. angusta). 



A. angusta Greg. (Diat. of Clyde, p. 38, pi. 4, f. 66*), plate 

 24, fig. 674. 



Frustule small, linear, elliptic, narrow, apices truncate. Ventral margin of 

 valve straight, raphe very inflexed. Part of valve narrow, stria? very delicate, 

 not distinctly beaded, about 17 in i c.d.m. Sutural zone very narrow. 



Marine. Scotland (Greg.) : Shores of North Sea. 



