No. 2328. PLEISTOCENE VERTEBRATES IN UNITED STATES— HAT. 97 



Family EQUIDAE. 



EQUUS COMPLICATUS Leidy. 



One tooth and several fragments of bones are referred to this spe- 

 cies. A milk molar of the upper jaw, with the inner half split oS, is 

 in the lot (Cat. No. 9158). It had just begun to be used. The width 

 at the summit is 34 mm. ; but at the base, 30 mm. A piece of the 

 upper end of a tibia, 5 inches long is eroded and somewhat crushed. 

 A fragment of the lower end of a tibia about 100 mm. long, has been 

 much gnawed by rodents. The two fragments probably belong to- 

 gether. There are also one first phalanx, lacking a part of the distal 

 end ; a nearly complete second phalanx and fragments of two others ; 

 also a pisiform bone. These have belonged to a very large horse. 

 The tibia measures 47 mm. across the hinder face; that of a recent 

 horse of medium size measures 40 mm. at the same place. The first 

 phalanx measures across the proximal end 55 mm. These bones have 

 the catalogue numbers 9159-9163. 



Some yeai-s ago ^ a tooth of a horse that had been found in the red 

 earth of a stone quarry near Cavetown and sent to the United States 

 National Museum for identification was regarded as belonging prob- 

 ably to Equus comylicatus. 



EQUUS GIGANTEUS? Gidley. 



Plate 4, fig. 1. 



With the Cavetown collection are found two fragments of the 

 upper left second premolar (pi. 4, fig. 1) of a large horse which is 

 referred to this species. The two pieces (Cat. No. 9164) were cer- 

 tainly parts of the same tooth, and they seem to fit together accu- 

 rately as placed in the figure. This tooth had been worn down to a 

 height of about 20 mm. The hinder part is missing, especially on 

 the outer side ; also most of the inner face in front of the protocone. 



The type of this species, found in southwestern Texas, is an upper 

 second molar, and it is especially distinguished by its large size, 

 having a length of 40 mm. or more on the grinding surface. As 

 shown by Gidley's figures,^ the enamel of the fosettes is rather 

 strongly folded. The length of the premolar from Cav.etown can 

 only be estimated. This premolar in a large horse (No. ,843, 

 U.S.N.M.) is 40 mm. long, and the distance from the rear of the 

 protocone to the front of the anterior fossette is 23 mm. In the Cave- 

 town specimen the latter measurement is at least 29 mm. and may be 

 as much as 33 mm. We may conclude that the whole length was 

 close to 50 mm. The width can not be exactly determined. The dis- 



1 Bull. 4. Dept. Archaeol. Phillips Acad., 1908, p. 12. 

 = Bull. Amer. Mus. Nat. Hist., vol. 14, p. 137, fig. 27. 



18140-1— 21— Proc.N.M.vol.58 7 



