The Rev. W. Smith on the Diatomacese. 9 



also noticed a cii'culation of the granular contents analogous to 

 that which is seen in many of the Desmidiece, and in the cells of 

 the higher orders of water-plants, a further proof that it is a 

 single cell, and a presumptive evidence of its vegetable nature. 

 With the aid of the parabolic reflector^ faint strise may be de- 

 tected on the surface of the valves. 



Plate II. fig. 1. S. biseriata: a, side view of frustule; b, front view of 

 ditto ; c, connecting membrane ; d, end view of frustule a ; e, transverse 

 section of empty frustule ; /, silex of connecting membrane after mace- 

 ration in acid ; g, apertures of costal canals seen in front ; h, view of the 

 ftustules on the completion of self-division. 



Surirella splendida, Kiitz. Frustule on front view oblong-ovate 

 with rounded ends ; side view ovate, with one end rounded and 

 the other somewhat acute ; alse large, costse distinct. Average 

 length of valve y^^ of an inch, greatest breadth of ditto ^^^ 

 of an inch {v. v.). 



Navicula splendida, Ehr. Infus. tab. 14. fig. 1. Surirella splendida, 

 Kutz. Bacill. p. 62. tab. 7. fig. 9 ; Phy. Ger. p. 72 ; Sp. Alg. p. 39. 

 Freshwater. Living. " Brooks " near Lewes ; Ashdown Forest, 



Sussex. Fossil : Lough Mourne deposit, very abundant ; Dolgelly 



earth, plentiful. 



Neai'ly the same in size as S. biseriata, but easily distinguished 

 from that species by its ovate form both on the front and lateral 

 view. The specimens from the Lough Mourne and Dolgelly 

 deposits are so much larger that they might be taken for a dif- 

 ferent species, but intermediate forms are so often found, that I 

 conclude the larger frustules are merely older and more developed 

 examples ; it is remarkable that in many of these latter the costal 

 canals do not appear to reach the central line. 



Plate II. fig. 2. S. splendida : a. lateral view of frustule ; b, front view of 

 ditto ; fig. 3. valve from Lough Momne deposit*. 



* Since this article has been in the printers' hands^ I have met with the 

 following species which appears to be undescribed : — 



Surirella constricta, mihi. Frustule on front view oblong with rounded 

 ends; outline on side view elliptico-lanceolate, each margin having a 

 central sinus ; alae distinct ; costae numerous, delicate ; medial fine inflated 

 in the centre. Average length of valve ^^ of an inch, breadth at con- 

 striction about f ^(f of an inch {v. v.). 



In brackish water neai* Lewes, 1850. 



The front view of this species bears a close resemblance to the same 

 aspect in S. biseriata, differing only in the appearance of the costse, which 

 in the present assume the character of stria: rather than ribs. On the side 

 view the constriction of the margins, the inflation of the central furrow, and 

 line-hke appearance of the costae, afibrd sufficiently distinctive characters. 

 The supei-ficial obsei-ver, regarding the side view only, might indeed con- 

 found this species with immature specimens of Cymatopleura solea, but a 

 slight examination shows that the resemblance is one of outhne merely. 



