Bl 

 densed outcr layer. Lcngth 0.014J-0.058 mm. (usuallyo.oo2-o.oo3 

 mm.), breadth of the girdle face 0.0114-0.023 mm., breadth of the 

 valve 0.007-0.009 mm. (usually 0.008 mm.). 



Locality: Atlantic coast of N. America (Atlantic City, New Jer- 

 sey) C), very common ! Black sea (Sebastopol), very rare. 



Small but very robust and characteristic species. In small indivi- 

 duals the breadth of the frustule sometimes surpasses its length, 

 and the lower end is in such cases very broad and sometimes (espe- 

 cially in specimens from the Black seaj excavated or concave-quite 

 the opposite of L. politica, where the inferior apex of the frustule 

 is rounded. 



27. L. pacifica Mer. 



Valve broad, cuneate, ovoide in small individuals, gradually ta- 

 pering from the summit which is broadly rounded towards the nar- 

 row and subacute inferior apex, margins s^traight. Pseudoraphe and 

 striae distinct, the latter about i 1-12 in o.oi mm. Girdle face broadly 

 cuneate, with upper angles rounded, outlines strong, inferior apex 

 broad. Septa comparatively deep (o.oo5 mm.), moderatly arcuate, 

 septal puncta round, very distinct. Endochrome granular. Sessil form. 

 Length 0.026Ó-0.0437 mm., breadth of the frustule 0.02ÓÓ-0.034 mm., 

 breadth of the valve 0.0081-0.0095 mm. 



Locality: California (San Fedro), not rare. 



This species has a certain resemblance to L. Lyngbyei, to which 

 it seems to be allied. The valves of large specimens resemble some- 

 what those of L. Jurgensii var. capensis Grun., but the septa are 

 much deeper, than in the latter. 



28. L. parasitica Mer. [fig. 19]. 



Valve rather narrow, somewhat abruptly attenuated towards the 

 lower end which is narrow, produced and with acute apex, upper 



(1) It is through the kindness of M.r Ch. Boyer of Philadelphia that I am 

 in possession of a pure gathering of this species from Atlantic City (New Jersey), 



