MERYCHIPPTJS. 



123 



Type. — Acad. Nat. Sci. Phila. Coll. (cast Amer. Mus. 10770.) (Leidy, 1857) "Founded upon a first and second 

 molar of the upper jaw of a remarkable equine animal, in the structure of the teeth approximating the ruminant family." 

 (Gidley, 1907) "Two right upper milk molars, dp 2 and dp 3 , in a fragment of the maxillary." Measurements: (Gidley 

 1907) dp 2 a.p. .022+, tr. .0175; dp 3 a.p. .022, tr. .019. 



Type figure. — Text Fig. 97 of this Memoir. 



Characters. — (Leidy, 1857) "The teeth are inserted by distinct fangs; and the crowns strikingly resemble the true 

 molars of ruminants. There are four demiconoidal lobes holding the same relationship with one another as in the latter, 

 especially as in the Deer. The outer lobes have almost the exact form as in the true molars of Orcodon. The inner lobes 

 resemble those of ruminants, but are complicated with accessory folds as in the horse.' No cementum fills up the inter- 

 spaces of the lobes nor does it appear to have existed as part of the structure of these teeth." 



This is the genotype of Merychippus. Although founded on milk teeth, the genus is well characterized. The species 

 awaits final determination. Its characters are (Osborn, 1918) : (1) absence of cement on the deciduous teeth; (2) brachyo- 

 dont, intermediate size; (3) small, pear-shaped form of deuterocone and tetartocone; (4) metaloph and hypostyle ptychoid 

 and continuous; (5) protoconule simple, crescentic; (6) external ribs well marked on ectoloph. 



Fig. 97. Original figures of the type of Merychippus insignis Leidy, Acad. Nat. Sci. Phila. Coll. (cast Amer. Mus. 

 10770), deciduous premolars of the right side, dp?, s. Natural size. After Leidy, 1S69, PI. xvii, figs. 3-4. 



PROCAMELUS-MERYCHIPPUS CALAMARIUS ZONE. 12. UPPER LEVELS. 



This zone is typified in the Santa Fe marls of New Mexico. 



Merychippus calamarius Cope 1875. 



Plates 11.4, 17.8, 18.2,6. Text Fig. 98. 



Hippotherium calamarium, Cope, sp. nov., Cope, E. D. "On Some New Fossil Ungulata," Proc. Acad. Nat. Sci. Phila. Vol. XXVII, 

 1875 (sig. dated July 27, 1875), pp. 259-260, no figure. Same description in "Report on the Geology of that Part of Northwestern New 

 Mexico Examined During the Field-Season of 1874, by E. D. Cope, Paleontologist and Geologist," Appendix LL, Ann. Rept. Chief of 

 Engineers in Ann. Rept. Geogr. and Geol. Surveys and Explorations West of the 100th Meridian, in Nevada, Utah, Colorado, New Mexico, 

 and Arizona (Wheeler), 1875, p. 70, no figure. "Report upon the Extinct Vertebrata obtained in New Mexico by parties of the expedition 

 of 1874," etc., Geogr. Surveys West of the One Hundredth Meridian (Wheeler), Vol. IV, Paleontology, 1877, pp. 321-322, PI. Ixxv, figs. 1, la. 



Horizon and locality. — (Cope, 1875) San Ildefonso, Santa Fe marls, Procamelus zone, New Mexico. Type collected 

 by E. D. Cope. (Cope, 1889, p. 451 1 ) " The II. calamarium has been found especially abundant in the Loup Fork beds of 

 Pojuaque near Santa Fe, New Mexico." 



1 Cope, E. D. "A Review of the North American Species of Hippotherium," Proc. Amer. Philos. Soc. Vol. XXVI, June 5 and Sept, 

 11, 1889, pp. 429-458, figs. l-24a (p. 451). 



