MADE BY DR. ANTONIO RAIMONDI IN PERU. 267 



my own. I trust that before long the studies of Prof. Hyatt on this question will 

 be published. 



A. Sp. indet. PI. 36, f. 2. 



A single specimen, too imperfect for detailed description. The shell is allied 

 to A. JRenauxianus, d'Orb., and A. cultratus, d'Orb. of the Neocomien. It is more 

 strongly carinated on the dorsum than the former, and the ribs, instead of being 

 bifurcated from a tubercle as in that species, are large and single. In this last 

 respect, as well as in the rib being more acute, it differs from the latter. 



Locality. From the " Cerro de Potosi." From the calcareous sandstone which 

 overlies the limestone of the Cerro of San Antonio; near the silver mines; height 

 4200 metres. 



The geological age is not stated, but the type of the species indicates either 

 the Jurassic, or a horizon very low in the Cretaceous. 



A. AEGOCEROS? Phil. PI. 36, fig. 3, 3a, 3b. 



A. aegoceros, Phil., Yiaje Atacama, p* 142, pi. 2, f. 2, 3. 



Shell many whorled ; whorls regularly rounded on the back and sides ; umbilicus 

 wide ; aperture subcircular. Surface marked by numerous, small, acute ribs, which 

 begin on the inner margin, and cross the dorsum ; these ribs arch slightly forward 

 on the middle of the side and on the dorsum. Most of them bifurcate in the 

 middle, though an occasional one, placed at irregular distances, remains entire. In 

 some cases, instead of branching, there is a secondary rib interpolated, its inner 

 end not uniting with that on either side. Septum unknown. 



Locality. On the label, with a corresponding number, one specimen is referred 

 to the Hacienda of Macanga, Prov. of Pataz ; but the accompanying catalogue, 

 as well as the label on another specimen with the»same number, gives "between the 

 Pueblos of Huandoval and Corongo, Prov. of Conchucos, Jurassic." The latter 

 is more probably correct, since there are other fossils from the former locality, and 

 their lithological character is entirely different. 



liemarks. The species is nearest to A. annulatus^ Sby. of the Lias, and A. biplex, 

 Sby. of the Oxford. From the former it differs in the ribs being fewer, larger, and 

 in being arched, instead of straight, and in more of them branching. The cross 

 section of the whorl is also much more nearly circular. In this last respect, it 

 also differs from the latter, as well as in having the ribs smaller and more 

 numerous. I have referred the species to Philippi's name doubtfully, since the 

 ribs on his figure seem to be straighter, but the figure is evidently badly drawn, 

 and the difference is too slight to warrant a separation. 



