DESCRIPTIONS OF FOSSILS. 



HY J. s. KKWBKRRT. 

 DELTODUS MERCUREI, Newb. 



Plate III, iigs. 1, I". 



Teeth of medium size, thick and strong, cuneiform or spatulate in outline, strongly 

 arched in both senses, broader end uniformly rounded, lateral margins thickened and 

 rounded over, on one side depressed, on the other raised into a prominent marginal 

 ridge, which is separated from the central portion of the crown by a relatively deep 

 and narrow sulcus; whole surface of crown finely punctate, especially in the sulcus, 

 and gently undulate. This is quite unlike any Coal-Measure Deltodus hitherto dis- 

 covered. In its general proportions and appearance, it is perhaps most like D. spatula- 

 iits, N. & W., from the Mountain limestone of Illinois; but in the present species the 

 marginal sulcus is much deeper and more conspicuous, and the granulation of the sur- 

 face finer. 



Formation and locality. Coal-Measures ; Santa FC", New Mexico. 



PTYCITOWS WIIIPPLEI, Marcou. 



Plate III, figs. 2-2'. 







Teeth varying in form according to their places in the mouth; largest, conical in 

 profile ; the central cone" rounded above and on the lateral and posterior faces, expanded 

 below into a flattened, subquadrate base; summit of crown marked with a few distinct, 

 acute, transverse folds of enamel; anterior face covered with reticulate, radiating, raised 

 lines, as in Pt. Mortoni; upper surface of margins of base finely and reticulately 

 wrinkled; tuberosity of base small, subquadrate, with a broad sulcus, having an 

 antero-posterior direction; the smaller teeth are rel||fvely broader and lower, elliptical 

 or subtrigonal in outline; the central cone marked with a few coarse interrupted ridges. 



This is the most conical tooth of the genus, the central cone being considerably 

 higher and narrower than in Pt. altior, Ag. The other known American species, Pt. 

 Mortoni, has also a decidedly conical form, in that respect differing from the European 

 species, but wants the transverse folds so characteristic of the flattened, quadrate spe- 

 cies of the Old World. 



In the specimen figured by M. Marcou, the crown is worn smooth, the folds being 

 all gone. It is also more angular than those now figured; but the general resemblance 

 is so strong that I do not hesitate to consider them the same. 

 18 s F 



