MADE BY DR. ANTONIO RAIMONDI IN PERU. 213 



little on the middle of the sides, and then cross the dorsum continuously. These 

 are rarely branched, but one or even two supplementary ribs are interpolated on 

 the dorsal half of the shell. 



Measurements. Greatest diameter, 2.05 in.; greatest width of body whorl, 1.1 

 in.; width of mouth, 1.3 in.; height of aperture from dorsum of included whorl, 

 0.65 in. 



Locality. " Province of Tarapaca, in the south of Peru." Jurassic. This is 

 evidently a stray specimen, since there is no exact locality given, nor the altitude, 

 nor yet even a guess at the geological age. This shell, also reported from Chili 

 and Bolivia, is of especial interest, since it assists us to fix the horizon of what 

 seems to be an important formation in the Andes. 



A. ACUTissiMUS, n. s., PI. 36, fig. 4, 4a. 



Shell discoidal, sides compressed, dorsum expanded and acute ; whorls slightly 

 convex on the sides, and marked by two rows of large rounded nodes, one near 

 the umbilical margin, the other towards the dorsum. These nodes are placed so 

 that the outer and inner row alternate, and they are connected with each other 

 by broad, faint undulations. Above the outer row of nodes the sides are concave. 

 Septum unknown. 



Measurements. Width of body whorl, 1.1 in.; width of aperture, 0.5 in. 



Locality. "Eidge of the three crosses, between Huallanca and Aguamiro ; 

 Prov. of Huamalies. Height more than 4000 metres. From a pulverulent car- 

 bonate of lime that appears to be Cretaceous." 



Remarks. This description is from a single small fragment, so imperfect that 

 I should not have felt warranted in describing it, were it not of so marked a form 

 as to run little risk of being mistaken. Its knife-like dorsum and the broad 

 nodes on the sides are characters which will separate it at a glance from any species 

 known to me. Hyatt says of it: "If this is from the Cretaceous, it may be closely 

 allied to my Buchiceras serratum, but it is not probably the same." 

 A. Ventanillensis, n. s., PL 39, fig. 2, 2a-d. 



Shell flattened discoidal; back broad, whorls increasing very gradually in size, 

 but slightly enveloping; aperture subquadrate ; umbilicus broad. Very young 

 shell smooth, without ribs, sides rounded, back with a small median keel, and each 

 whorl enveloping about half of its predecessor. At a little over an inch in 

 diameter, the shell acquires large rounded plain ribs, the tubercles beginning to 

 appear on the fifth or sixth rib. In the adult individuals, with the volutions 

 nearly two inches wide, the surface characters are entirely difi"erent. The umbilical 

 margin is rounded, and gives rise to numerous, closely placed, rounded ribs, starting 



