The Rev. W. Smith on the Diatomacese. 7 



therefore by gravity directed towards the surface of the glass and 

 the eye of the observer. When the connection of the parts is 

 dissolved by an acid, a single valve may often be detected with 

 its disc uppermost, when the character of the cost^ and the 

 smooth portion in the centre of the valve may be readily de- 

 tected. I am indebted to the discoverer of this species m this 

 country for numerous specimens gathered by him m l«4a, ana 

 again in 1850. 

 Plate I. fig. 2 a. C. spiralis in its ordinary position; b, a detached valve. 



CampyMiscus cribrosus, mihi. Valves orbicular; disc marked 



^vith radiating lines of minute perforations, crowded towards 



the margin. Average diameter of valve ^io ^^ ^n inch {v. v.). 



In brackish water, shores of Poole Bay, 1848. 



This is probably identical with C. Echeneis, Ehr., but I am 



without a figure to assist in its identification ; and the words of 



the 'Species Alganim,' " disco medio Isevi sohdo," do not apply to 



the present species, the perforations in ours extending over the 



entire surface, though more distant and somewhat scattered in 



the middle. 



Plate I. fig. 3. C. cribrosus : a, surface of valve ; b, view showing con- 

 necting membrane. 

 Campylodiscus parmlus, mihi. Valves orbicular; disc traversed 

 by two parallel ridges ; strise about twelve, nearly parallel. 

 Average diameter j^q of an inch {v. v.). 

 Poole Bay, 1848. 



This species is readily distinguished by its minute size and 

 the ridges on its valves, which are very prominent in certain 

 positions of the frustule. It does not appear to have been noticed 

 either by Kiitzing or Ehrenberg. 



Plate I. fig. 4. C.parvulus: a, disc of valve; b, view presenting the 

 connecting membrane and valvular ridges. 



SURIRELLA, Turp. 



Valves concave, with a longitudinal central line and margins 

 produced beyond the suture (winged). Erustules free, solitary, 

 or when undergoing self- division, in pairs. 

 The concavity of the valves, their winged margins, and the 

 longitudinal central line, which wants the central depression so 

 conspicuous in the Naviculece, are characters which sufficiently 

 distinguish Surirella from all other genera. I believe a careiul 

 examination of the lories, when deprived of their coloured con- 

 tents, would detect the presence of al« in all the species. 1 

 have certainly recognized them in six, viz. S. hismata splen- 

 dida, striahda, gemma, fastuosa and a'attcula, and 1 thmk there 



