KITTON, ON DIATOMACE^. 15 



injured valve Actinocyclus [Eupodiscus, Smith) Ralfsi (var. 

 E. sparsiis of Gregory), that portion of the valve upon 

 which the pseudo nodule occurs was, I suspect, broken oif, as 

 the author says it was an imperfect specimen, or it may have 

 been overlooked as it is sometimes very minute. This is 

 commonly the case with the Coscinodiscus Barklyi of the 

 Yarra Yarra deposit and which is, I believe, identical with 

 C.fuscus ; both are species of Actinocyclus (the presence of a 

 pseudo nodule is not recognised by Ehrenberg). 



Stauroneis costata, O'M, fig. is, I think, a sporangial 

 state of Achnanthidlum lineare. 



The valves of Cocconeis, like those of Arachnoidiscus, 

 Actinoptychus, and some other genera, are composed of two 

 (generally) dissimilar plates ; the upper valve (both plates) 

 and the lower plate of the lower valve have neither median 

 line nor nodule, while the upper plate of the lower valve has 

 both, and when the two valves are united, we see the median 

 line and central nodule of the lower through the upper valve 

 and imagine it belongs to the upper. All figures hitherto 

 published are imperfect in so far as they do not give — 1st, 

 both valves in conjunction, 2nd, upper plate of the upper 

 valve, 3rd, lower plate of ditto, 4th, lower valve, 5th, upper 

 plate of ditto, 6th, lower plate of ditto. Occasionally two or 

 three species present precisely the same aj^pearance in the 

 lower plate of each valve, and the chief characters are 

 therefore to be got from the upper plates of the two valves. 

 But we cannot contrast any figure of the two valves with 

 either an upper or lower valve separated, nor one of these 

 with the other. It will thus be evident that any description 

 of new species from a single specimen or even series of 

 specimens procured from deposits or dredgings must be 

 erroneous. 



Cocconeis Portii, O'M, fig. 7, Vol. VII, n. s., shows both 

 valves in conjunction and appears to be a small state of 

 C. scutellum. 



Raphoneis Uburnica, O'M, fig. 8, is the upper valve of a 

 Cocconeis, but of what species I am not able to say ; it may 

 probably be C. distans, W. Gregory. 



R. suborbicularis , O'M, fig. 9, is one of the plates of the 

 upper valve of Cocconeis Grevillii. 



R. Jonesii and R. Moorii, O'M, figs. 10 and 11, are both 

 the upper valves of one and the same species of Cocconeis, 

 perhaps C. scutellum. The absence of the hyaline margin in 

 fig. 10 is of no specific value, it has possibly become detached, 

 an accident of frequent occurrence; Cyclotella rotula and 



