10 The Rev. W. Smith on the Diatomacese. 



Swirella striutula, Turp. Frustule on front view wedge-shaped 

 with rounded extremities ; side view broadly ovate ; alte small ; 

 costEe few, about fourteen, conspicuous. Average length of 

 valve giy of an inch, greatest breadth of ditto ^^^ of an inch 



{v. v.). 



Navicula striatula, Ehr. Infus. tab. 21. fig. 15. Sitrirella striatula, 

 Kiitz. Bacill. p. 62. tab. 7. fig. 6 ; Phy. Ger. p. 72 ; Sp. Alg. p. 39. 

 In the sea or brackish ditches. Poole Bay, 1848 ; near Pevensey, 



Sussex ; near Hull, Mr. R. Harrison ! Rye, Mr. Jenner ! 



I have not been able to insert a front view of this species 

 without excluding from the plate other more important figures ; 

 this aspect of the present species however presents no feature of 

 importance, and the lateral view is sufficient to distinguish it 

 from our other native forms. 



Plate III. fig. 1. S. striatula, lateral aspect of the valve. 



Surirella craticula, Ehr. Frustule on front view oblong with 

 centre slightly inflated ; side view lanceolate with acute ends ; 

 alse large ; costse few, distinct, divergent. Average length of 

 valve 2^0 ^^ *^ inch, greatest breadth of ditto -^j^ of an inch 

 {v. s.). 



Kiitz. Bacill. p. 61 . tab. 28. fig. 22 ; Phy. Ger. p. 71; Sp. Alg. p. 35. 



Freshwater. Bramley near Guildford, J. R. Capron, Esq. ! In a 

 slide labelled " River Bann, Ireland," sent me by Mr. Cocken ! 



Approaches S. biseriata in its lateral aspect, and the regular 

 development of its connecting membrane, but well distinguished 

 fi'om that species by its smaller size, fewer costse, about twenty 

 on each side of the central line, and by the absence of these from 

 the middle part of the valve. The divergence of the costse is also 

 a peculiarity not found in the former species. 



Plate III. fig. 4. /S. craticula : a, front view of the frustule ; h, side view 

 of ditto. 



Surirella fastuosa, Ehr. Frustule on front view slightly wedge- 

 shaped with rounded ends ; side view ovate ; al?e small ; costse 

 few, apertures of the costal tubes large ; medial line inflated 

 in the centre. Average length of valve ^^^ of an inch, greatest 

 breadth of ditto gi^ of an inch {v. v.). 



Kiitz. Bacill. p. 62. tab. 28. fig. 19 ; Sp. Alg. p. 38. 

 Poole Bay, 1848. Coast of Sussex, 1850. 

 The large round openings of the costal canals, and the smooth 



central portion of the valve, give to this little species a peculiar 



and beautiful appearance. The valves are deeply concave. 



Plate III. fig. 3. S.fastuosa : a, lateral view of the frustule ; b, front view 

 of ditto. 



