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



Var. fructa ScuuM. (1862). — V. almost symmetrical, gibbons in the middle, from which it 

 tapers to the ends. L. 0,o34 to 0,047; B. 0,(jo5 to O.oo? mm. Stria", in 0;ii 1 mm. — Gomph. 

 fractum Schum. P. L). p. 187 f. 32. 



Fresh and brackish water: Konigsberg, Baltic (Schum.), Caspian Sea ((Iran.). 



2. R. Van Heurckii Grun. (1881). — V. slightly clavate or broadly lanceolate, obtuse. 

 L. 0,007 to 0,00'j; B. 0,003 to 0,00."^ mm. Upper V. with broad, lanceolate area, and radiate mar- 

 ginal stricB, 14 to 15 in 0,oi mm. Lower V. without distinct area, and radiate strite, 18 in 0,oi 

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



Fresh water: Belgium (V. H.). 



Anorthoneis Gtrun. (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 striffi. 



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 crihrosa. 



1. A. excentrica Donk. (1858). — V. orbicular, 0,025 to 0,o4 5 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. Striai 10 in 0,oi mm. radiate throughout, in the middle alternately longer 

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

 rows. Striffi and puncta closer towards the margin, about 13 in 0,oi 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 ai'ea in- 

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

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



Marine, jEstuaries: Firth of Tay! English Channel! Mount Desert Island, Maine! 

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



2. A. eurystoma Cl. N. Sp. — Upper V. almost orbicular, about 0,o4 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,oi mm., composed of puncta, larger towards the area (about 

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

 rows. — PI. Ill f. 12. 



Marine: Pensacola! 



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

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

 neis coccotieiformis N. Sp. It seems to be nearly allied to the symmetrical Cocconeis Kinheri 

 A. S. Atl. CXCI, 37. 



Campyloneis (trun. (18G2). 



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

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

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

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

 plicated structure. 



