JOHNSTON, ON DIATOMACE.E. 19 



can judge from the sketch unaccompanied by the description, 

 or notice of the number of costae in - 001, agrees perfectly 

 ■with Gephyria incurvata, so that presumptive evidence is 

 strongly in favour of the propriety of reducing my Gephyria 

 to Entopyla, and to this conclusion I some time since had 

 arrived ; but on again examining with great care what 

 Ehrenberg says, I am now compelled to relinquish this idea, 

 and shall here quote from Ehrenberg, as translated in the 

 'Ann. Nat. Hist./ 1818, p. 343: "It (Entopyla) forms 

 quadrangular plates, which, seen from the side, are rounded 

 off above and below. These quadrate tablets or boxes consist 

 of several leaves like a book, which, however, are perfectly 

 connected. The leaves are parallel with the narrow sides 

 and curved ; the two external leaves are like the cover of a 

 book, thicker, and marked with thirty-two longitudinal ribs. 

 The concave outer leaf is upon the ventral side, since it ex- 

 hibits two large roundish apertures at the extremities ; the 

 opposite convex leaf has no aperture ; all the intervening 

 leaves have a large aperture in the centre, leaving only a 

 thin margin ; thus forming a large continuous space in the 

 interior of these little boxes. The structure of Biblarium 

 (Tetracyclic of Smith) is similar." 



He adds, under the specific character : " In adult specimens 

 the middle leaves are almost {fere) sixteen in number, the 

 costse of the lateral leaves more than forty, separated by a 

 flexuous median line." From Ehrenberg in these descrip- 

 tions speaking of middle and outer leaves, wdthout any other 

 distinction than those indicated, it appears to me that all these 

 were similar in general appearance ; in short, that the middle 

 leaves were what Smith calls annuli, as in Rhabdonema and 

 Tetracyclic, and not merely the connecting zone, dividing 

 into lamellae or thin slices, as are seen in some species of 

 Amphiprora, &c. Now Gephyria differs from Eupleuria by the 

 want of these cellulate annuli, and if Ehrenberg' s description 

 can be relied on, and it is too detailed to admit of a doubt, his 

 Entopyla austrdlis can neither be a species of Gephyria nor 

 any species of Eupleuria known to me, and a question may 

 even arise if it belong to Eupleuria at all ; it seems a con- 

 necting link between Eupleuria and Rhabdonema, from which 

 last it is distinguished by the dissimilarity of the valves or 

 outer leaves of Ehrenberg. 



As to that from Elide guano, fig. 9, I have only examined 

 one perfect frustule and a few valves. It was first brought 

 under my notice in September, 1858, by Mr. A. M. Edwards, 

 of New York, who then informed me that he had detected 

 it in guano from Elide Island, California, about eighteen 



