18 



an examination of the type ppeeimens would be necessary for a satis- 

 factory comjiarison. The group, as a whole, may be convenient!}' 

 arranged as follows : — 



A. Umbilicus small, oj- entirely closed. 



B, Umbilicus comparativel}' lai-ge. . 



1852, " Nautilus elegans, Sowerby." 



Rfemer's " Kreidebildungen Von Texas," page 37, No. 37. 



No descrijjtion or figure of this shell is given, and all that is stated is 

 that " some imj^erfect sj^ecimens from the waterfall of the Guadaloupe, 

 below New Brauenfels, plainl}^ show the peculiar, undulating, arclied 

 ribs on the surface, characteristic of this species." 



1860. Nautilus Texanus, Shumard. 

 Transactions of the Academy of Sciences of St. Louis. Vol. I., page 190. 



As the specimens from which this species was described are mere 

 fragments, which do not show the characters of the umbilicus, it is 

 not certain to which of the divisions proposed above it should be 

 referred. 



The shape of the aperture of JV. Texanus is not unlike that of N. elegans, 

 (Sow.) but the position of the siphuncle is the same as in N. pseudo- 

 elegans, the species with which Dr. Shumard compared it. 



1862. "Nautilus elegans. Sow., vai-. Nebi*ascencis," Meek. 



Proceedings of the Academy of Sciences of Philadeljjhia for 1862, page 25. 



In the paper where this Nautilus is descriljed, Mr. Meek, naturally 

 enough, seems to have taken the correctness of D'Orbignj-'s and 

 Sharpe's identifications for granted, without further im^uiry. The 

 description of the Nebraska fossil, at least, accords much better with 

 that of iV. Atlas (nobis) than with Sowerbj^'s diagnosis of his iV. elegans. 

 The globose shape, together with the position of the siphuncle in the 

 American shell, are in favour of this view, but it is possible that the 

 varietal name, proposed by Mr. Meek, may have to be raised to specific 

 rank, as the sculpture of the so-called " variety ISlebrascensis'' is said to 

 consist of ribs which are " five times as broad as the grooves between," 

 and in this respect it difters fi-om N. Atlas, as well as from nearly 

 related species. 



