262 Professor T. Rupert Jones — 



Adult carapaoe-valves, broadly subovate in outline. Length 8"3, 

 height 5-6 mm. Young forms, subtriangular or suboblong. Its 

 resemblance to -E". Gihoni is mentioned at p. 78, op. cit. 



The original was from Mangali in Central India, probably of 

 Ehajtic age. Dr. Geinitz's specimens (see above) were from Challao 

 and elsewhere ^ in the Mendoza province of the Argentine Republic ; 

 accompanied by M Forbesii if we take Geinitz's fig. 5, pi. i (1876), 

 to represent the latter species. Of the six figures referred by 

 Dr. H. B. Geinitz to M Mangaliensis (op. cit. 1876), one, namely 

 fig. 4, seems to represent this species, and figs, 1 and 2 may also 

 belong to it. 



Concentric Ridges. Meshes from Eidge to Eidge. 



U. Dahalacensis 14-15 . . . 6-7 



E. Gihoni 14-15 . . . 6-7 adult, but not so old as the others. 



E. Mangaliensis 16-17 . . . 7-8 



E. Forbesii 22-23 . . . 17-18 



Tj. Forbesii (numbers imbedded in a brownish shale) was brought 

 to England by David Forbes in 1861 from Cacheuta, in the province 

 of Mendoza. 



Professor Philippi'a specimens of F. Mendocina, referred to 

 further on, also came from near Cacheuta in Mendoza. It bears 

 a close resemblance to E. Forbesii, and measures 11 x 8 mm. 



§ IV. Stelznek; Cacheuta, 1885. 



The Cerro de Cacheuta, on the eastern slope of the Andes, 3500- 

 4000 feet above the sea, is about twenty miles S. by W. of 

 Mendoza city (33° S. lat.), in the Argentine Eepublic. Its 

 geological structure is shown in Stelzner's map and sections 

 (pi. iii) in his " Beitrage zur Geologie und Palaeontologie des 

 Argentinischen Eepublik," I, Geologiseher Theil, 1885, p. 76, etc. ; 

 in Fischer's " Palasontographica," Suppl., iii, Lieferung ii, Heft 1, 

 " Ueber die geognostischen Verhaltnisse der Umgegend voa 

 Mendoza," etc. 



This hill of Cacheuta consists mainly of gneiss and mica-schist, 

 with a central mass of intrusive igneous rocks (" trachyte, andesite, 

 and basalt "). On one flank of the hill strata of variegated sand- 

 stone, with clay and carbonaceous shale, lie in a broken synuline 

 with steep sides. These beds are referred to the Khsetic series. 



§ V. Philippi, 1887. 



In his " Die Tertiaren und Quataren Versteinerungen Chiles," 

 etc., 1887, Dr. E. A. Philippi described and gave some small 

 figures of two kinds of Fstheria, p. 223, pi. l, figs. 11 and 12. The 

 little outline, fig. 11 (16 x 12^ mm.) is described as a suborbicular 

 form, like " Fstheria Dahalacensis'' (probably by accident or error), 

 slightly oblique, very thin, almost flat, with irregularly concentric 

 wrinkles ; one margin nearly straight, with the umbo at two-fifths 

 of its length. Philippi named it Estheria ? Chilensis (reproduced 



1 Of the six specimens it is stated, at p. 16, that they came from Agua de la 

 2orra, Challao, Agua salada, Cerro de Cacheuta, and San Lorenzo. 



