272 GOMPHONEMA. 



Median stride much shortened, the others radiant up to the apices, 9 to 10 in 

 1 c.d.m. Length, 4 to 8 c.d.m. 



Fresh water. Rare. Alle (Delogne), Ard. Lig. (De Wild.). 



var. subclavatum Grun. (H.V.H. Atl., pi. 23, f. 38* ; in Type 196), 



plate 7, fig. 304. 



Differs from the type form by the undulations being feebly marked or 

 absent, the valve being often only slightly inflated at the median portion. 



Fresh water, Rare. Namur (P. Gautier), Alle (Del.) 



var. commutatum Grun. (H.V.H. Atl., pi. 24, f. 2* ; Type No. 

 211), plate 7, fig. 305. 



Differs from the last variety, into which it passes imperceptibly, by its 

 shorter and gently lanceolate form. 



Fresh water, Brussels (Delogne). 



bb. Valve rostrate-lanceolate. 



G. parvulum Kiitz. (Baa, p. 83, pi. 30, f. 63 ; h.v.h. Atl., pi. 25, 



f. 9* ; in Types Nos. 25, 206, 211, etc.), plate 7, fig. 306. 



Valve cuneate-lanceolate, with apices rostrate tapering. Stria? nearly reach- 

 ing to the raphe, the median one much shortened, the others of equal length, 

 radiant, about 14 in 1 c.d.m. Length, 2 to 3 c.d.m. 



Fresh water. Common. 



var. lanceolata. (H.V.H. Atl., pi. 25, f. 10*). plate 7, fig. 307. 

 More elongate and more narrowly lanceolate. 



var. subcapitata. (H.V.H. Atl., pi. 25, f. 11*), plate 7, fig. 308. 

 With upper rostrum slightly capitate. 



Prof. Cleve considers the G. viicropus described below as a mere variety 

 of G. parvulum. 



aa. VALVE HAVING NEAR THE CENTRAL NODULE A HYALINE AREA MORE 



OR LESS STAURONEIFORM. 



b. At least one of the atices of the valve sub-acute. 



G. gracile Khr. (Inf., p. 217, No. 307, pi. 18, f. 3; G. naviculoirfes 

 W. Sm. ; H.V.H., pi. 24, f. 12, 13, 14* ; Type No. 212), plate 7, fig. 309. 



Valve lanceolate, rhomboidal, elongate, with apices almost similar. Raphe 

 surrounded by a distinct area, dilated into a kind of pseudo-stauros at the 

 median portion. Nodules slightly distant from the apices. Strise feebly 

 radiant, about 9 or 10 in 1 cd.ro. Length, 3^5 to 9 c.d.m, 



Fresh water. Mozaive (Delogne). Ard. Lieg. (De Wild.). Edinburgh, Scotland (W. Sm.). 

 Holland (Suringar). 



