166 P. T. CLKVE, SYNOPSIS OF THE NAVICULOID DIATOMS. 



Var. fracta Schum. (1862). — V. almost symmetrical, gibbous in the middle, from which it 

 tapers to the ends. L. 0,o34 to 0,047; B. 0,oo5 to 0,oo7 mm. Strife 9 in 0;oi mm. — Gompk. 

 fractum Schum. P. D. p. 187 f. 32. 



Eresh and brackish water: Königsberg, Baltic (Schum.), Caspian Sea (Grrun.). 



2. R. Yan Heurckii G-run. (1881). — V. slightly clavate or broadly lanceolate, obtuse. 

 L. 0,007 to 0,009; B. 0,003 to 0,005 mm. Upper V. with broad, lanceolate area, and radiate mar- 

 ginal strise, 14 to 15 in 0,oi mm. Lower V. withont distinct area, and radiate strii©, 18 in 0, 01 

 mm. — V. H. Syn. p. 127 Pl. XXVI f. 5 to 9. 



Fresh water: Belgium (V. H.). 



Anorthoneis Grun. (1867). 



Valves dissimilar, orbicular. Upper valve without central nodule and median line, but with 

 an excentric axial area. Lower valve with excentric median line and central nodule. Structure 

 of both valves similar: puncta arranged in radiate striae. 



This genus was proposed by Grunow (Nov. p. 9) for Cocconeis excentrica Donk., the closer 

 affinities of which species are obscure, although there is some resemblance in the structure to 

 Mastogloia cribrosa. 



1. A. excentrica Donk. (1858). — V. orbicular, 0,025 to 0,045 mm. in diameter. Upper 

 valve with a narrow axial area not reaching to the margin and dilated in the middle to a small, 

 rounded central area. Strise 10 in 0, 01 mm. radiate throughout, in the middle alternately louger 

 and shorter, distinctly punctate; puncta 10 in 0, 01 mm. forming longitudinal or irregularly oblique 

 rows. Strife and puncta closer towards the margin, about 13 in 0, 01 mm., which gives the valve 

 the appearance of being bordered with a rim. Lower V. thinner, with distinct median line, the 

 ends of which do not reach the margin. Central pores approximate. Axial and central area in- 

 distinct. Striation as in the upper valve. — Coccon. excentr. Donk. T. M. S. VI p. 25 Pl. III 

 f. 11. A. S. Atl. exem, 57. 



Marine, sestuaries: Firth of Tay! English ehannel! Mount Desert Island, Maine! 

 This species lives free among the sands of the beach, not attached to algaj. 



2. A. eurystoraa Cl. N. Sp. — Upper V. almost orbicular, about 0, 04 mm. in diameter. 

 Axial area large, lanceolate. Strise throughout radiate and alternately longer and shorter, 14 (at 

 the margin) or 10 (at the area) in 0, 01 mm., composed of puncta, larger towards the area (about 

 10 in 0,01 mm.) than at the margin (about 12 in 0, 01 mm.) and forming undulating longitudinal 

 rows. — Pl. III f. 12. 



Marine: Pensacola! 



Of this species I have seen some few upper valves only, but Grunow sent me, many years 

 ago, a shetch of a similar valve with central nodule and median line under the ms. name of Alloio- 

 neis cocconeif armis N. Sp. It seems to be nearly allied to the symmetrical Cocconeis Kinkeri 

 A. S. Atl. CXCI, 37. 



Campyloneis Grun. (1862). 



Valves dissimilar, in outline elliptical or orbicular. Upper valve without central nodule 

 aiifl median line, with radiate rows of coarse puncta or alveoli. Lower valve with central nodule 

 and median line, with radiate, finely punctate striie. Between both valves, and connected to the 

 lower valve by some vertical processes, is an interiör silicious skeleton of more or less com- 

 plicated structure. 



