8 Prof. W. Smith on the Diatomacese of the Pyrenees. 



A form somewhat larger than the present, and with fewer 

 strise, occurs in the Aberdeen gatherings of Drs. Dickie and 

 RedferD, containing Orthosira Dickieii, Thw., Synop. B. Diato- 

 macese, vol. ii. p. 60. This I am disposed to refer in like manner 

 to the species above described. 

 Plate I. fig. 3. S. V. of Tryhlionella gracilis /3. 



Navicula scita, n. sp. Valves nitescent ; S. V. linear-elliptical, 

 attenuate towards the extremities. Striae slightly inclined, 

 very faint, 45 in -001". Length -0012" to -OOSJi". Greatest 

 breadth of V. -00033". v. v. 



Fresh water. At higli elevations in the Pyrenees : Lac de Gaube, 

 5866 feet ; Lac Gave de Lizez, 3000 feet ; Mt. Hormigas, 5250 feet ; 

 near the Mahourat Source, 3804 feet ; Lac d'Estom, 6566 feet. 



Plate II. fig. 4. S. V. of Navicula scita. 



Navicula Pyrenaica, n. sp. S. V. linear-lanceolate, slightly in- 

 flated at the extremities. Strise obscure. Length 'OOl 1" 

 to -0017". Greatest breadth -0002". v.v. 



Fresh water. Gave de Lizez near Cauterets, elevation 2634 feet ; 

 Gave de la Reine, elevation 2696 feet. 



Plate II. fig. 5. Side views of Navicula Pyrenaica. 



Navicula dissimilis, n. sp. Frustule oblique ; S. V. elliptical ; 

 median line somewhat diagonal from the obliquity of the 

 frustule, recurved at its extremities. Striae obscure. Length 

 •0009". Breadth -0003". v.v. 



Fresh water. Mt. Pechineya near Cauterets, elevation 6222 feet ; 

 Lac de Gaube ; cascade near St. Sauveur, elevation 3020 feet. 



Notwithstanding the beautiful pink colour of the dry valve, 

 indicating the presence of markings on its surface, I have been 

 unable to resolve the strise of this species so as to estimate their 

 number. 

 Plate II. fig. G. Side views of Navicula dissimilis. 



Cocconema lanceolatum, Ehr. Synopsis of the British Diato- 

 maceae, vol. i. p. 75. 



Var. /3. Convex margin much elevated, subangular. Length 

 of valve -0042" to -0058". Greatest breadth of ditto -0016". 



Var. J. Valve nearly direct, linear towards the rounded extre- 

 mities. Length of valve '0053". Greatest breadth of ditto 

 •0009". v.v. 



Fresh water. Gave de Lizez ; Gave de la Heine near Cauterets. 



