MADE BY DR. ANTONIO RAIMONDI IN PERU. 269 



A. CORNIFERUS, n. s., PI. 38, fig. 1, la. 



Shell flattened and converging on the sides, and flattened and grooved on the 

 dorsum ; whorls enveloping nearly one-half; umbilicus moderate ; aperture nearly 

 twice as broad at its widest part (across the dorsum of the enveloped whorl) as at 

 the top. Surface marked by dichotomous ribs, which run from the umbilical 

 margin and branch about the middle of the side. At the point of division, there 

 are tubercles on some specimens, which are, however, absent on others. From this 

 point they arch forward with a slight and regular curve, bearing (or not, according 

 to variation) a slight tubercle on the dorsal margin. In one case, between each 

 pair of bifurcated ribs, there is a supplementary rib interpolated, beginning on the 

 line of division, and continuing to the margin, in all respects like the branching 

 rib. From the mould in the matrix, it can be seen that the ribs were acute, and 

 the tubercles were armed with spines. In one specimen there is no trace of ribs 

 crossino- the dorsal groove ; in another it is crossed by obsolete ribs, while in a 

 third they are as well developed here as on the sides. Septum unknown, beyond 

 the fact that it consists of a dorsal lobe, two large ones on the sides, a large 

 ventral, and some small details about the umbilical angle. 



Measurements. Greatest diameter, 3.0 in.; width of body whorl, 1.4 in. (ap- 

 proximate); greatest width of aperture, 1,1 in.; width of the aperture at the 



dorsum, 0.6 in. 



Locality. " Five leagues southeast of the village of Recuay, Dept. of Huaraz. 



Height 3500 metres. Jurassic." 



Remarks. Three specimens imbedded in calcareous nodules, from which it is 

 impossible to extract them, so as to show satisfactorily the umbilical region. The 

 species is nearest allied to A. Garantianus, d'Orb., of the Lower Oxford, but 

 differs in having a broad, regularly concave groove on the dorsum, and in the 

 shape of the cross section of the whorl. In one shell the greatest width is below 

 the middle of the aperture, above which there is a rapid convergence of the sides. 

 There are also other minor differences in the details of ornament, especially in the 

 presence of spines, and the sharper ribs in one shell. 



A. CARBONARius, h. s., PI. 38, fig. 2, 2a, 2b. 



Shell large, flattened discoidal, slightly convex on the sides, converging rounded 

 towards the dorsum, which is acute ; whorls deeply enveloping ; umbilicus small. 

 There is very little difference in general appearance between the young and adult 

 shell, the characteristic markings on a shell of 0.75 inch in diameter being pro- 

 portionately stronger, but exactly like one of nearly 8 inches across. Surface 

 marked by numerous regular ribs, slightly flattened on their upper surftice, and 



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