298 F. B. Loomis — Osteology and Affinities 



levels the skeletons are pretty much disassociated, while in the 

 upper level, when a specimen is found, it is usually a more or 

 less complete skeleton. Above these levels there is nothing 

 approaching a bone bed, but occasionally Stenomylus remains 

 are, however, found throughout the whole thickness of the fine 

 sandstones. The even sorting and bedding of these sands indi- 

 cate deposition in comparatively quiet water ; and as the Lower 

 Harrison beds seem to be flood-plain deposits, it would appear 

 that these finer sandstones were laid down in some more shel- 

 tered area behind a barrier, which barrier must have been of 

 considerable extent and height to account for the deposition of 

 about 100 feet of uniform material. The Stenomylus remains 

 presumably floated to their final resting place, and each of the 

 two bone-bearing levels represents the destruction of scores of 

 individuals. The simplest reconstruction of conditions would 

 picture a herd of the unfortunate creatures during the distress 

 of a great flood taking refuge on the highest available point of 

 land ; which, however, proved too low, and after surrounding 

 them the rising waters drowned and carried off the whole 

 herd, males and females, young and old. The carcasses then 

 floated down stream and were accumulated in the backwater, 

 where they were then buried in the accumulating sands. This 

 was apparently a relatively rapid accumulation, for the carcasses, 

 especially in the upper level, are not pulled to pieces by carni- 

 vores. The position of the head in the type (fig. 1) is charac- 

 teristic of a good many of the skeletons, and I believe is common 

 among drowned animals. Presumably the same point of land 

 in two seasons proved to be a fatal trap for herds of these deli- 

 cate creatures, and afterward it was only occasionally that an 

 individual carcass was washed into the area where these sands 

 were accumulating. Remains of other animals are very scarce 

 in these sandstones, but a few isolated bones, the Dicerathe- 

 rium, and the major part of a skeleton of Daphamodon 

 superous Peterson, and a few bird bones do occur with the 

 Stenomylus bones, and confirm the stratigraphic determination 

 of Lower Harrison. 



Plan. — In considering the material it seems best to give a 

 detailed osteological description of this species, followed by the 

 distinctive comparisons of the three known species, and finally 

 to consider the affinities and phylogenetic position of the 

 genus. 



Stenomylus hitchcocki sp. nov. 



Type. — The type is a complete skeleton, all the bones articu- 

 lated and in place, No. 2059 of the Amherst College collection. 

 With this are used six skulls and a dozen upper and lower 

 jaws, together with some four disarticulated skeletons and iso- 



