MAPE BY DR. ANTONIO RAIMONDI IN PERU. 



265 



the umbilical margin and develop into a rather sharp tubercle. From this tubercle 

 they run entire, or branch into two or even three, each ending on the dorsal margin 

 in a small tubercle. As the shell increases in size, the umbilical row of tubercles 

 changes in character, they becoming fewer and much more prominent, and the 

 sides of the shell more convex. UmbiHcus nearly a fourth of the diameter of the 

 shell, its margins rounding off with a regular curve into the sides between the 

 nodes. Dorsum* flattened, rendered concave by the two dorsal rows of tubercles 

 which are placed alternately. Aperture subovate, deeply notched by the preceding 

 whorl. Septum comparatively simple, consisting of a dorsal and eight lateral 

 lobes, with their corresponding saddles. The lobes are all small ; the dorsal is 

 short and broad, ending in two short branches, with all the teeth of nearly the 

 same size, as are those on the sides of the lobe; the middle space between, the 

 branches is about one third of the depth of the lobe, and of an equal width. The 

 entire lobe lies in the space on the dorsal surface between the tubercles. The 

 superior lateral lobe is not more than half the length of the dorsal, very constricted 

 above, and is expanded below into a spathalate form, bordered by six or seven 

 teeth nearly of the same size. The dorsal saddle is divided by a deep notch into 

 two unequal parts, the upper side indented by four teeth, the lower by but one. 

 The first two lateral lobes are, like all the others, of the same shape as the superior 

 lateral, but of twice the size, and end in five bidentate processes. The second and 

 third saddles are notched by one tooth each, the fourth by two, and the others by 

 but one each. The other lobes are of the same general pattern as already described, 

 but diminish regularly in size and become correspondingly more simple in detail, 

 except one on the margin of the umbilicus, which is of the same size as the third 

 lateral. 



Greatest diameter, 4.5 inches; greatest width of whorl, 1.7 in.; width of aper 

 ture, 1.5 in.; width of umbilicus, 1.0 in. 



Locality. Quebrada de Huari, between Morococho and Jauja. "From a bluish 

 calcareous sandstone extensively developed in the Cordillera of the central part of 

 Peru. Jurassic. Height of 3300 metres above sea level." Attached to it in the 

 same block of matrix is a fragment of Neithea b-costata, and a small Exogyra 

 (young 0^ E. polygonaf). The presence of the former shell proves it to be middle 

 Cretaceous. 



The present species is of the type of A. Micheliniaiius, d'Orbigny, of the French 



* I use the term dorsum, in accordance with the old usage, for the peripheral portion of the shell, although 

 recent research seems to point to this having really corresponded with the abdominal aspect of the animal. In 

 doing so, I have no other defence to offer than that this entire paper has been written some time, and before the 

 publication containing these new views reached me. 



