Naviculacea.'] infusoriat, animalcules, 430 



with a nuicli attcnuatctl acute apex, its figure, laterally, recalling 

 that of the tongue of birds. 



Genus Sphexella (Kiitz). — Frustules on piimaiy side cuncato, 

 free, -without stipes, and unattached ; not enclosed by any common 

 gelatinoias investment. 



Along with Gomphonema and Splicnosira, constitutes the family 

 Gomphonemccc, differing from the first in not being stallccd, and from 

 the second in its decided cuneate figure, and in not forming similar 

 sti'aight chains. 



The several species are marine iu habit and pretty generally dis- 

 tributed, none of them arc identifi.ed by Kiitziug with any forms 

 described by Ehrenberg. 



S. glacialis. — Small on secondary side, lanceolate, with very fine 

 transverse strife. Length 1-1 320th. Among Conferva. Monte Rosa. 



S. vulgaris. — Small ; very obtuse, on secondary side {dorsum, Ehr.), 

 dilated at the middle, and finely striated. Length l-1020th. In 

 fresh water ponds among Algas. 



S. ohtusata. — Small on secondary side, expanded above the centre, 

 quite smooth; apices round and obtuse. Length 1 -900th (P. 17, 

 f. 31). Ponds. Nordhausen. 



S. angustata. — Small, slender, narrowly cuneate and linear, con- 

 joined in a flabelKfonn manner ; on secondary side, quite smooth, vciy 

 obtuse at the apex, rather dilated above the centre. Length l-960th 

 (PI. 17, f. 30). Nordhausen. 



S. rostellata. — Solitary, very smooth, broadly wedge-shaped ; on 

 secondary side, dilated centrally, acuminate at each end. Leni-th 

 l-1020th to l-720th. 



Yar. (J), dongata. — Lai'ger; the apices produced and obtuse. 

 Length l-720th to l-336th. Both found in freshwater. Nordhausen. 



S. (?) parvula. — Small, very smooth on secondary side, lanceo- 

 late, acuminate at the apex, rather dilated at the produced base. 

 Length l-960th. Yery like Gomplionema. Ealaise. 



S. (?) Lenormandi. — Small, navicular, very smooth ; on primary side 

 linear and truncate ; on sccondaiy, lanceolate and acute. Length 

 1 -960th. Freshwater. Falaise. 



This species presents navicular bodies intermixed with delicate 

 fibres, and probably belongs to JVavicuIa. 



