Cope.] I" [May 16, 



Measurements. M. 



Diameters of M. ii { anteroposterior 017 



I transverse 014 



HOLOMENISCUS, gen. nov. 



Under the tiead of this genus I give a synopsis of the results of my 

 studj^ of the extinct Camelidoe of the American Pliocene epocli. I can 

 compare the specimens from Buenos Ayres with those from Mexico and 

 Oregon, and Branco and Owen have given detailed descriptions of speci- 

 mens from Buenos Ayres and Mexico. From these sources I learn of the 

 existence of the following generic forms of Camelidae. I omit Protolabis 

 Cope,* and refer it to a separate family — the Protolabididae, on account 

 of the presence of three superior incisors in eacli premaxillary bone, as 

 in the primitive Ruminantia, combined with the presence of a cannon 

 bone. 



I. Premolar teeth |. 



P-m. i separated by diastemata Procamehis. 



II. Premolar teeth |. 



P-m. ii below wanting PUaiichenia. 



III. Premolar teeth f . 



Fourth inferior premolar triangular Camelus. 



Fourth inferior premolar composed of two crescents, which enclose a lake 



(an inferior P-m. 3 ?) Palauclienia. 



Fourth inferior premolar composed of two crescents, with two posterior 



tubercles behind them Pi^otauchenia. 



IV. Premolar teeth f 



Fourth premolar below triangular Auchenia. 



V. Premolar teeth \ 



Fourth superior premolar composed of two crescents Holomeniscus. 



Fourth superior premolar consisting of a simple cone Eschatius. 



The position of this genus being determined as above, it remains to 

 examine the material representing it, at my disposal. 



In 1873 Dr. Leidyf described a large species of llama from specimens 

 from California, which include the entire inferior series of molar teeth, 

 and one superior molar. The first inferior molar, properly the fourth pre- 

 molar, has the crown partiallj^ worn, showing that it was opposed by a 

 grinding tooth in the superior series. In the Museum Nacional of Mexico 

 is preserved a complete mandibular ramus, containing all the teeth of one 

 side of an animal smaller than Dr. Leidy's type, but having a general 

 resemblance to it ; including the worn fourth premolar. In the collections 

 of Professor Condon and myself from the Oregon desert, there are vari- 

 ous isolated molars agreeing in measurements with Dr. Leidy's type, and 

 belonging probably to the same species. In the Condon collection is part 



* Proceedings Academy Philadelphia, 1876, p. IJo. 



t Report U. S. Geol. Survey Terrs., F. V. Hayden, 1, p. 255, pi. xxxvii, figs. 1-3. 



