JOHNSTON, ON DIATOMACE.E. 17 



Asteromphalus, as defined by Dr. Greville,* and from the 

 genera Asteromphalus and Asterolampra, as described by 

 Ehrenberg.f The rays differ from any hitherto recorded 

 species of Asteromphalus, whilst the areolated segments, 

 being all equal and similar, and connected with the centre 

 by what Mr. Johnston calls the secondary ray, would seem 

 to show greater affinity to Asterolampra. It will require a 

 careful examination of many more than the single specimen 

 recorded by the author before its position can be safely 

 decided on. 



Campylodiscus productus, Johnston. — A careful comparison 

 of the description and figure of this species with those given 

 of Surirella lata by Professor Smith, J and an examina- 

 tion of the variations that occur in any good gathering 

 of that species, will, I think, leave little doubt that they are 

 identically the same. The number of canaliculi is stated by 

 Professor Smith to be 3 or 4 in '001, and in his figure 

 there are 33 in all; in Mr. Johnston's species there are 

 37. The length given by Professor Smith is -0041 to -0062, 

 whilst Mr. Johnston states his to be '0058. The only dif- 

 ference appears to be in the length of the canaliculi and in 

 the " crescent" of granules in the centre ; but as the markings 

 and canaliculi are subject to considerable variation in most 

 species of Surirella, this would be no good ground for specific 

 distinction. 



Campylodiscus marginatum, Johnston (fig. 1 1) . — The generic 

 position of this species is doubtless correct, but whether it can 

 be safely considered a new species from the examination of a 

 single valve may be questioned, as the only characters that 

 would distinguish it from the C. limbatus of M. De Brebisson§ 

 are the greater separation of the canaliculi, and the more 

 strongly marked central area. In outline and general charac- 

 ter they are closely allied. Professor Gregory proposed the 

 same name for a species he detected in the dredgings from the 

 Clyde, but on consideration adopted the name already pub- 

 lished by M. De Brebisson, and has given figures and descrip- 

 tion. || The markings of the central area are a point of little 

 specific value, as has already been pointed out in regard to 

 Camp. Hodgsonii.%. 



Cocconeis regina, Johnston (fig. 12) . — This appears to be cor- 



* ' Micr. Jour.,' vol. xxvii, p. 100. 



f ' Berlin Proceedings,' 1844, pp. 73, 198. 



% ' Synopsis,' vol. i, t. ix, f. 61. 



§ ' Diatomees de Cherbourg,' p. 12, t. i, f. 1. 



|| Gregory, 'Marine Diatoms of the Clyde,' t. iii, f. 5. 



% ' Micr. Jour.,' vol. vi, Trans., p. 86. 



