I 



180 p. T. CLEVE, SYNOPSIS OF THE NAVICULOID DIATOMS. 



Var. alpestris Br. (1880). — L. 0,027 to 0,033; B. 0,012 to 0,oi5 mm. V. truncate, with 

 strongly sigmoid axial area, dilated in the middle to a large subquadrate central area. StrirE 

 about 23 in 0,oi mm. Lower V. with small central area, stricB about 25 in 0,oi mm. — Ach. flex. 

 B. D. des Alpes PI. Ill f. 2(i. Diatomiste II p. 72 PI. V f. 15. 



Alpine regions: Switzerland! Norway (Br.), Auvergne (Br.J. 



Disconeis Cl. N. G. 



Valves in outline elli])tical, without marginal rim, very dissimilar. Upper valve coarsely 

 costate, with narrow axial area. Lower valve without axial area, and with punctate radiate stri<e. 



The forms placed in this genus are not closely connected. As to their affinities it may be 

 noted that the lower valve of C. Lyra perfectly resembles a small form of Navicula Hennedyi, 

 and that of C. reticuhtfa a small form of the section Puuetutce of Navicula. The lower valve of 

 C. pinnata has a great resemblance to C. Fediculns or C. pscudomarginata, and C. formosa in its 

 lower valve recalls C. costata. 



Artificial hey. 

 Costffi of the upper valve anastomosing into a reticulum 2. 



) Axial area narrow, lanceolate C. formosa Brun. 



I — — a silicious rib C. reticulata Cl. 



Axial area of the upper valve very narrow 4. 



— — — — — lanceolate 5. 



{ 



. j Costse alternating with double rows of coarse puncta C. Lyra A. S. 



I — crossed by fine oblique striae C. Itexayona Br. Cl. 



^ J Costae alternating with rows of short lines C. versicolor Br. 



1 — — — double rows of fine puncta C. piniiata Greg. 



1. A. hexagona Br. a. Cl. (1891). — Outline bi'oadly linear, with cuneate ends. L. 0,042; 

 B. 0,02 mm. Upper V. with very narrow axial ai'ea. Stria^, 11 in 0,oi mm., parallel in the 

 middle, radiate at the ends, crossed by a set of close obliqixe striie, about 25 in 0,oi mm. Lower 

 V. with very narrow axial area. Median line straight; central nodtxle transversely dilated to a 

 stauros not reaching the margin. Strife 13 in 0,oi mm., transversely lineate, strongest near the 

 margin, faint on other parts of the valve. ^ D. especes nouv. p. 5 PI. XIX f. 3 a, b. 



Marine: Western Africa and Nossibe (Brun.), Yokohama (Brun Coll.)! 



The lower valve has some resemblance to 0. costata, Xnxi the upper differs in its structure, 

 and especially in the absence of the marginal ring. 



2. C. Lj'ra A. S. (1874). — Outline elliptical. L. 0,023 to 0,o6; B. 0,oi4 to 0,033 mm. 

 Upper V. without area, but with an axial rib sending off on both sides parallel (at the ends 

 radiate) costtie (about 7 in 0,oi mm.) alternating with double rows of puncta, about 15 in 0,oi 

 mm., forming longitudinal rows. Lower V. with straight median line, and transverse central area, 

 united on both sides to a broad linear area, so as to form a lyre-shaped figure. Strire 15 in 0,oi 

 mm. not distinctly punctate. — N. S. 1). p. 93 PI. Ill f. 19 (right figure, lower valve). (J.? 1. c. 

 f. 18 (upper figure, upper valve). C. noroegica Orun. Cl. M. D. N:o 102 (1878) upper valve. 



Marine: Grip and Bergen, Norway! 



This curious and isolated form has exceedingly different valves, which I have fouiul to- 

 gether in the same frustule. The lower valve resembles a small form of Navicula lleiuwdyi 



3. C. reticulata Cl. N. Sp. — Outline elliptical. L. 0,03 to 0,035; B. 0,017 to 0,02 mm. 

 Upper valve with an axial rib sending off, laterally, transverse costtB (about 6 in O.oi mm.) ana- 



