202 CEETACEOUS PERIOD. 



Diameter of the only example in the collections, the larger part of the 

 outer chamber being broken away, fourteen centimeters. 



Specific name given in honor of Dr. Oscar Loew. 



Position and locality. — Strata of the Cretaceous period ; Ojo cle los 

 Cuervas, New Mexico. 



Ammonites placenta Dekay var. intercalaris Meek and Hayden. 



Some more or less imperfect specimens of this species are contained 

 among the collections from Gallinas Creek, New Mexico. A small portion 

 only of the external surface is shown, but this contains in part the charac- 

 teristics by which Meek and Hayden separate the variety intercalaris from 

 the typical forms of the species as pu.blislied by Dekay. It agrees with 

 the variety above referred to also in being less compressed than the typical 

 foims of A. placenta are. 



Gentjs BUGHICEEAS Hyatt, 1875. 



Buchiceras Swallovi Shumard. 



Plate XX, fig. 1 a, 5, and c. 



Ammonites Swallovi Shumard, 1860, Trans. St. Louis Acad. Sci., i, 591. 



Shell moderately large, flattened-discoid ; sides gently convex ; dorsum 

 narrowly flattened, • the flattened space bordered on each side by a row of 

 more or less distinct nodes; volutions thi'ee or four, partially embracing; 

 umbilicus broad, its outline not clearly defined, deep for so discoid a shell, 

 although it has a shallow aspect because of its breadth and want of definite 

 outline, and exhibiting a large part of each of the inner volutions ; aper- 

 ture subovate in outline, its longest diameter directed from the center of the 

 shell, narrowest at the outer end, where it is trancated by the flattening of 

 the dorsum ; sides of the volutions marked by prominent, somewhat flexuous, 

 romided costse, extending from the inner to the outer edge ; the space 

 between each two of these principal costse is occupied by one or two short 

 ones which do not reach the umbilicus, but they end at the dorsum like the 

 others ; upon each costa, near its dorsal end, there is an obtuse node, which, 

 together with the dorsal nodes before mentioned, constitute a double row 



