Paleontology Zorritos Formation 49 



leaves open the possibility that a different systematic posi- 

 tion may be found necessan-. The Xassidae are in a bad 

 state as regards the crystallization in the literature of differ- 

 ential characteristics, and the revision that is necessary is 

 naturally without the bounds of this work; without such 

 revision the designation of a new unit to receive this shell 

 would only add to the confusion which now awaits the atten- 

 tion of a reviser. 



The most closely allied species known to the writer is 

 A^assa veneris Fauj., of the Burdigalian of the Gironde, 

 France, and the Mediterranean Tertiary, described by Bell- 

 ardi,*- and later referred by Cossmann *^ to the genus Dor- 

 saniim Gray. Reference to the type of Gray's genus shows 

 that iV. veneris probably does not belong to it, and it is ap- 

 parent that iV. zorritensis and A', veneris are of a sub-group 

 yet to be designated, differing from Xassa chiefly in being 

 strongly keeled, with a distinct shoulder giving a squarish 

 aspect to the upper parts of the whorls and of the aperture. 

 Most of the Xassas have a stronger callus than have the two 

 forms here discussed, and it is probable that that feature will 

 prove a further point of differentiation. 



Variegated Zorritos. South of Quebrada Pantheon. 



Genus Triumphis Gray 

 Triuinphis solida (Xelson) 



Plate II — Fig. 3. 

 Clavella solida Xelson, Trans. Conn. Acad., vol. 2, p. 199, 1870. 



Pyriila roscta Grzj-bowski, Xeues Jahrb., Beil. Bd. 12, p. 648, 

 pi. 19, fig. 6, 1899. 



"Shell oval, ventricose, and heavy ; spire moderately ele- 

 vated and tapering. Whorls five to seven, more or less 

 depressed above. Sutures distinct. Body whorl large, more 



'Piemonte, pte. 3, p. 58, pi. 4. figs. 3a. b, 1882. 

 ' Essais de Pal. Comp., vol. 4, p. 219, 1901. 



