EDENTATA OF THE SANTA CRUZ BEDS. 273 



MEASUREMENTS. 



Type. No. 9,241. No. 9,575. No. 15,314. 



Mandible, length of predental beak 021 .027 .026 



" depth below ^ 030 .028 .030 



" thickness below ff .016 .017 .017 



" length condyle to ? 052 .052 .049 



Except in a few details, the vertebrae (Plate LVII, fig. i) are very 

 similar to those of Hapafaps. The atlas is broader in proportion to its 

 length, a difference which is principally due to the larger size of the trans- 

 verse processes ; the neural arch is narrower antero-posteriorly, not ex- 

 tending over the posterior pair of cotyles and more distinctly emarginate 

 between the anterior pair ; the latter are quite closely approximated and 

 ventrally are separated only by a deep and narrow notch ; the inferior 

 arch is slender and has a more prominent hypapophysis than in Hap- 

 alops, while the transverse processes are longer and have a more reg- 

 ularly curved free border. The neural spine of the axis is much larger 

 than in the last named- genus, extending well over the atlas. In the other 

 cervical vertebras the principal difference from Hapalops consists in the 

 narrower neural arches and the larger neural spines and transverse pro- 

 cesses. In the anterior thoracic region also the spines are longer and on 

 the first and second vertebrae they are nearly erect. The posterior tho- 

 racics, lumbars and sacrals are not known. 



Associated with the American Museum specimen (No. 9,241) are nine 

 caudals from the anterior part of the tail and these are supplemented by 

 an individual (No. 15,314) in the Princeton collection, which has a num- 

 ber of the caudals, including a series of nine from the hinder part of 

 the tail, lacking not more than two or three terminal vertebrae; the full 

 number of caudals can therefore hardly have exceeded twenty or twenty- 

 one. As a whole, the tail is much like that of Hapalops, of moderate 

 length, but very heavy, rapidly tapering behind, while the individual 

 vertebras are of the type common to all of the known Santa Cruz Gravi- 

 grada; the centra diminish steadily in diameter, but very gradually in 

 length as far as the tenth caudal ; from the latter backward the decrease 

 in size is much more rapid and is accompanied by a marked depression 

 or flattening in the hinder part of the tail ; the facets for the chevrons are 

 very obscure, if present at all, on the first caudal, but each succeeding 

 vertebra to the ? fifteenth has two prominent pairs of such facets, the 



