FAUNA OP THE EQUUS BEDS. 85 



Measurements. 



H. Bul- n. heH- 



ciitus. ternus. 



Mm. Mm. 



Length of molar series 14G 157 



Length of true molars 122 134 



„.,,,. ( anteroposterior 25 35 



Diameters M. i < '■ __ .,_ 



( transverse 17 lb 



„ . i. HT • • ] anteroposterior 40 44 



DiametersM.il ] ^ 



( transverse 20 19 



-r^. , ,r ••• (anteroposterior 55 50 



Diameters M. iii •< ^ ^ ^ ■ -, i, , on i c 



( transverse of middle column 20 IS 



Depth of ramus at M. i 68 51 



Depth of ramus at M. iii, middle column 85 79 



Numerous bones of camels of size and character appropriate to this spe- 

 cies were found by the expedition, but positive reference can not be made 

 at present. 



HOLOMENISCUS MACROCEPHALUS, Cope. 



Sp. nov. Plate XXIII, Figure 5. 



This lama is determined from a nearly complete lower jaw. One ramus 

 is lacking in nearly all the parts posterior to the last molar, while in the 

 other these parts are present, lacking only the condyle and angular hook. 

 The dentition can be completely restored from one side or the other. 



This species is intermediate in dimensions between the H. vitakerianus, 

 Cope, and the A. lama, Linn, being smj,ller than the former in dental 

 measurements, and larger than the latter. The S3nnphysis mandibuli has 

 about the length of that of the A. lama, but the rami are considerably 

 more elongate, the extremity of the last molar in the A. lama reaching 

 only to the middle of the anterior column of the corresponding tooth of 

 the H. macrocephalus. I observe here that it is not certain as yet that 

 the species now described is not an Auchenia, as the superior dentition is 

 not known. 



The canine is separated from the third incisor by a diastema, which is 

 a little less than one-third the length of that wliich separates the canine 

 from the anterior premolar, and the latter is about equal to the dental 

 series, less the last molar. In its proporti<ms to the other teeth the pre- 

 molar is much like those of the A. lama, and is smaller than in the H. 

 vitakerianus. The disproportion in the sizes of the molars is not so gi-eat 

 as in the 11. sulcatus. As in the latter species, the internal wall of each 

 molar is slightly concave at the point of junction of the columns, but in 

 the second and third true molars this concavity is bounded in front by a 

 narrow ridge, which is wanting in the H. sulcatus, and in the first true 

 molar ofH. macrocephalus. A similar ridge exists at the front of the an- 

 terior column of the second and third true molars, as in A. lama. The 



