NATURAL HISTORY SOCIETY OF GLASGOW. 219 



with the strias very faint, but when made out by an excellent 

 microscope, these are only 47 in '001, j)recisely as in N. sigma. 

 The supposed ridges are merely the angles formed at the union of 

 the valves with the zone; and in A. sigmoidea the nitzschoid keel 

 on each valve raises the supposed number of ridges to six. 



I have mentioned that N. ciirvula of Smith has been now 

 removed to Surirella: to this it may be objected that SiirireUa is 

 characterised by the presence of transverse canaliculi in (or on) 

 the valve. If by canaliculi superficial furrows are merely meant, 

 this is nearly correct ; but elsewhere Smith appears to indicate by 

 that expression, tubes within the substance of the valve — as under 

 Epithemia; "the transverse costa?, I regard as minute canals, 

 which convey the nutrimental fluid to the surface of the internal 

 membrane." In Surirella there are no such internal tubes, but 

 the valve is much undulated, particularly near where the angle or 

 keel is seen; the portion beyond the keel is also undulated close 

 to the keel, the union of the two series of undulations at the keel 

 causing the singular appearance, well represented by Smith, in 

 S. biseriata, S. nobilis, S. splendida,''' and several others. This also 



* Allied to S. splendida, and confused with it by Smith, is a species which is 



now well known to collectors of slides as S. elegans, of which a broken valve was 



Hgured by Ehrenberg in his tab. amer. His >S'. flexuosa in that work appears 



to be the same species. At least I have seen narrow broken valves present the 



shghtly twisted appearance he represents. Both were obtained from the same 



samjjle from Eeal del monte. Kiitzing, in his Sp. alg., places them in a section 



of Surirella, corresj^onding to Campijlodiscits of others, and Eabenhorst places 



both in Campylodiscus, referring the last to 0. spiralis; and probably what 



Kiitzing obtained from Hildesheim in Germany, and considered <S'. elegans, was 



C. costatus. Mr Rylands and I, when we gave it the name of S. splendida, had 



seen no authentic specimens, but if the Mexican species be also this Campylo- 



discus, the name S. elegans may be retained. It is found in the deposit from 



Lough Mourne (Co. Antrim), and therefore is probably intended to be iigured 



by Ehrenberg, in his Mikrogeologie, tab. xv., under the name of S. ohlonga, 



which has been altered by Mr Carruthers, in Gray's Handbook of British 



Water Weed.s, p. 87, to S. bellis. I presume that Ehrenberg's sample is from 



Lough Mourne, from its containing Epithemia Hyndmanni (under the name of 



E. luna), and some other species found in that deposit (althoiigh he seems not 



to have observed Staur. punctata, characteristic of it) ; Ehrenberg says, that it 



was from the Mourne mountains, in the County of Do\vn, and that he got it 



from the Countess of Caledon. His second sample, or " probe," was no doubt 



from the Moiirne mountains, and is that known as " Lord Roden's plate 



powder," but I have seen no deposit, from the County of Down, at all similar to 



Ehrenberg's " erste probe," or first sample ; and have no doubt he was 



deceived by the name of Mourne being apphed both to the mountains of County 



