282 ACHNANTHES. 



in i c.d.m., and more strongly radiant, shortened and leaving an elongated 

 hyaline area, larger in the lower than in the upper valve. Length, from 1*5 

 to about 3 c.d.m. 



Fresh water. Virton (Delogne). France. England (Comber). 



A. minutissima Kutz. (Alg. aq. dulc, No. 75, Bac., p. 75, pi. 



13, f. 2 c, etc. ; H.V.H. Atl., pi. 27, f. 37 and 38* ; in Types Nos. 11 1 and 

 269), plate 8, fig. 334. 



Valves very narrowly lanceolate, with apices gently produced, rostrate, 

 obtuse, rounded ; striae delicate, feebly radiant, about 25 in 1 c.d.m., the 

 median shortened. Length, about 1*5 to 2 c.d.m. 



Fresh water. Brussels (Delogne), Ard. Lieg. (De Wild.), France, England. 



A. linearis W. Sm. (S.B.D., ii., p. 31, pi. 61, f. 381 ; H.V.H. 



Atl., pi. 27, f. 31 and 32*), plate 8, fig. 335. 



Differs from the preceding, into which it appears to pass, by its valves 

 being more linear, elongated, somewhat produced, rostrate, and its striae 

 somewhat stronger and sub-parallel, 24 to 27 in 1 c.d.m. Length, 1 to 1*5 

 cd.m. 



Freshwater. Brussels (Delogne). Scotland (W. Sm.). England (Kitton). Ireland (O'Meara). 

 bbb. Valve longly elliptic, inflated at the middle and at the apices. 



A. trinodis (Arnott) Grun. (H.v.H. Atl., pi. 27, f. 50, 51, 52*; 



Type No. 129; Achnanthidium trinode IV. Am. ; Rhoiconeis trinodis Grun. 

 olim), plate 28, fig. 788. 



Valve very small, longly and narrowly elliptic-sublinear, inflated at the 

 median portion and at the apices with subequal lobes and rounded apices. 

 Striae very delicate, 25 to 30 in 1 c.d.m., short, not reaching to the raphe, 

 which is robust. Central nodule elongated. Girdle face semi-flexed at the 

 median portion. Length, about 2*5 c.d.m. Breadth at the median portion, 

 6 c.d.m. (6/m.). 

 Fresh water. England (Norman), Scotland (W. Sm., W. Arn. !). 



a a. UPPER VALVE DIFFERING FROM THE LOWER BY THE PRESENCE, ON 

 ONE OF ITS MARGINS, OF A HYALINE SPACE IN FORM OF A 



HORSE SHOE. 



A. lanceolata Breb. (in Kutz. Spec Alg., p. 54; h.v.h. Atl., 



pi. 27, f. 8-1 1*; Type No. 235), plate 8, fig. 336. 



