210 S. CALVIN AFTONIAN MAMMALIAN FAUNA II 



200 millimeters (about 7% inches) ; height of coronoid, 102 millimeters 

 (about 4 inches) ; antero-posterior diameter of crown of canine at base, 

 23 millimeters; transverse diameter of same, 13 millimeters. 



Ungulates 



H0RSE8 



A great proportion of the new material simply duplicates and verifies 

 that previously known. In the collections horses still predominate, so far 

 as number of teeth and recognizable parts of the bony skeleton are con- 

 cerned. The majority of the teeth belong to the large species, which in 

 the first paper was identified with Gidley's Equus scotti; but at least one 

 large molar from the Turin pit agrees with number 117, which was noted 

 in paper I, page 350, as having dimensions which might justify its refer- 

 ence to Equus pacificus. Some of the equine phalanges and metatarsals 

 are certainly larger than those of the average domestic horse, and these 

 indicate the possibility at least of an Aftonian species outranking Equu^ 

 scotti in size. On the other hand, there are smaller molars of the E. 

 compUcatus type, and two inferior grinders from Aftonian beds exposed 

 in a cut on the line of the Illinois Central Eailroad near Sioux Falls, 

 South Dakota, are notably smaller than any of the corresponding teeth 

 from other localities. The specific relations of these last mentioned teeth 

 must await larger collections and fuller information. Two splint bones, 

 one from Turin and one from Missouri Valley, are parts of equine skele- 

 tons not previously collected. Though not deciding with certainty when 

 Pleistocene horses became extinct, it may be noted that in Iowa no equine 

 remains have yet been found in deposits younger than the Aftonian. 



On page 138 of the paper on the "Present phase of the Pleistocene 

 problem in Iowa" ^ there is brief notice of a small, slender limbed horse, 

 which is indicated by a few fossils collected from the Aftonian beds near 

 Afton Junction and Thayer (plate 19, figures 1-4). The fossils referred 

 to include an astragalus, the larger part of a metatarsal, a proximal pha- 

 lanx, and one or two unerupted teeth, from which no effort was made to 

 determine the enamel pattern. Inasmuch as no other mammalian remains 

 are known from the Thayer and Afton Junction pits, it was assumed that 

 these fossils might possibly be remains of some preglacial animal acci- 

 dentally included in the interglacial gravels, and so reference to them is 

 omitted from the paper published later on the Aftonian mammalian 

 fauna. Taking into account the history and genesis of the gravels, the 

 successive stages and conditions through which the bones must have passed 



Bull. Geological Society of America, vol. 20, March, 1909, pp. 133-152. 



