GASTROPODA. ' l ' 1 ". 



LfcMplm.1 



an- imt amply -utliri.Mit f..r thfir -.'pur.it urn ami r. rc^mt i<m ' 



as we have shown on pages 981- 939, un<l '.'41, and as may be seen from the figures 

 on pliito I.X V 1 1 1. has a very different aperture, being entirely without the peripheral 

 notch and hand. These differences are so important that the two genera cannot 

 possibly belong even to the same family. As to our Trepotptra, it resembles Liospira 

 greatly, and may really be, though we are much inclined to doubt it. a lineal 

 descendant of the Ixnver Silurian type. However that may prove to be, a generic 

 separation must always be maintained because of the changing characters of the 

 whorls of the spire and the short apertural slit which together characterize 

 Trepotpira and not Liospira. We refer the reader to page 957 for more detailed 

 observations on these points. 



When it comes to Eotomaritt, we are willing to admit something more than 

 mere resemblance. The form in that genus is more conical than lenticular, the 

 suture better defined, the lines of growth generally stronger, and the peripheral 

 band situated entirely upon the upper side of the edge, while the inner lip, so far as 

 known, is never reflected over the umbilicus as is so commonly the case in Liospim. 

 In the latter the sutures are nearly always enamelled and so that part of the band 

 is covered. In Eotomaria, on the other hand, all of the band is visible and the outer 

 edge of the inner whorls projects slightly above and over the inner edge of the next. 

 These differences, we believe, are quite sufficient to separate the two types of sheila 

 as distinct genera, especially as they hold their own without any appreciable 

 tendency to run into each other. Still, we believe that one was derived from the other. 



Of the two genera Liospira probably was the older. We come to this conclusion 

 because its band is of the convex type, which, it seems to us, is necessarily a more 

 primitive structure than the concave band. The convex form of band we believe 

 always points to an alliance with the Euomphalidit which, theoretically at least, are 

 older than the Pleurotomnriidir. Liospira undoubtedly began earlier than the Calci- 

 ferous, in which it was represented by at least one good species. What it was 

 derived from we cannot say at present, yet we feel convinced that Lophospira 

 originated in the same stock. As to the origin of Eotomaria we are not so confident, 

 still we are strongly inclined to regard it as evolved from Liospira. There is nothing 

 unreasonable about this belief, for that the necessary changes in the position and 

 character of the band may have occurred is indicated by L. decipiens, in which the 

 periphery is sharp and that portion of the band which lies on its upper side is not 

 only decidedly concave but much the greater part of the whole. 



We describe, and in most cases illustrate, a total of fourteen species of this 

 genus. Besides these we regard liaphisloma premium Whitfield (Calciferous), PUuro- 



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