NATURAL HISTORY SOCIETY OF GLASGOW. 213 



finding tliat it belonged to the genus Cocconeis, of Kiitzing's 

 Bacillarien, he proposed to change the name to C. amygdalina, 

 from its resemblance in miniature to the kernel of an almond : he 

 pubHshed neither names. Kutzing, however, had got specimens from 

 him under the nam^ of Frust. nidulaiis, and published it in his 

 Systema Algarum as Cocc. nidulaiis; this was done in 1849, tliree 

 years before Smith found his specimens at Jersey; so that the 

 name C. diaphana must, perhaps, be laid aside. Mr Ralphs, in 

 Pritchard's Infusoria, tells us that it is got "nidulating in mucous;" 

 this is a mere inference from the name; it is really not so. I may 

 add that M. de Brebisson has since obtained better specimens 

 from La Croisie, or the antheridia of Laurencia tenuissima. In 

 the same way Gregory's C. distans figured in the Clyde Diatoms, 

 f. 23, is merely the upper valve; the lower valve is probably very- 

 dissimilar. C. nitida, f. 26, of the same work, is also an upper 

 valve, the lower l^eing unknown, or, if described, it is under 

 another name. Another circumstance with regard to Cocconeis 

 ought to be noticed. Not only are the two valves usually very 

 different in appearance, but in several species, perhaps in all, 

 each valve consists of two layers or plates, which may be separated 

 by much boiling in acid, or being long in water after the alga has 

 decayed, as found in dredgings and deposits. As the two layers 

 are differently marked, we are liable to make several new species 

 on that account; the inner layer of the upper valve is generally very 

 pellucid, and also the lower one of the lower valve; but some 

 species have the lower valve considerably larger than the upper 

 one, the portion or margin beyond the upper one being strongly 

 marked, although the central part (covered by the upper) be 

 colourless. This extension or border appears to me in all cases to 

 belong to the lower layer of the lower valve; so that the upper 

 layer has a nodule and median line, and is only the size of the 

 upper valve, while the lower layer has the strongly marked 

 border or margin, although the middle part be diaphanous with 

 no, or only obscure stria3, and no nodule or median line. C. ornata 

 of Gregory is an example of a valve with this border; it is difficult 

 to say whether it represents the two valves conjoined, or only the 

 lower. 



Gregory's fig. 27, C. pseudomarginata, represents a small species 

 with both valves. His fig. 28, called by him C. major, is a larger 

 specimen of probably the same species, but exhibits the lower 



