306 W. B. Scott — Some new forms of the Dinocerata. 



tuberances aDd having only rudiments of the maxillary and 

 parietal protuberances. The supra-occipital is pierced by two 

 large venous foramina, placed one on each side of the median 

 line. 



The species may be called E. parvum and is defined by the low 

 supra-occipital and parietal crests, the long and very narrow 

 muzzle, the presence of a single tubercle on each molar tooth, 

 and the small size of the animal (see figs. 2 and 3). It might 

 at first sight be supposed that we have here the skull of a fe- 

 male or young animal, which would account for the very small 

 size of the so-called horns. But the complete and somewhat 

 worn dentition and the state of the sutures at once negative 

 the supposition that the animal was not entirely adult. The 

 question of sex is rather more difficult to decide. Professor 

 Marsh has shown that the skulls of female Dinocerata are 

 characterized by small canine tusks and less prominent " horns." 

 Professor Marsh very kindly allowed me to make a careful 

 examination of the female skulls in his collection, which imme- 

 diately convinced me that Elachoceras is not a mere sexual va- 

 riety of Uintatherium, as I had suspected might be the case. 

 The tusks are not only proportionally but actually of much 

 greater diameter than in very much larger females. In point 

 of fact, in proportion to the size of the skull, the tusks of Elacho- 

 ceras are nearly if not quite as large as in the largest Uinta- 

 therium males. On the other hand the protuberances are very 

 much smaller than in any known female and the nasal pair seems 

 to be altogether absent. I cannot, however, state this with 

 entire certainty, as the extreme tip of the nasals is broken off, 

 but the fact is more than probable for these reasons : (1) The 

 nasals are preserved beyond the tips of the premaxillae, where 

 in all other known Dinocerata the swelling for the protuber- 

 ance is visible. (2) In Elachoceras the nasals are exceedingly 

 thin and weak, whereas the nasals of Uintatherium are strik- 

 ingly strong and heavy ; in the former there is no trace of any 

 thickening or swelling at the tips of the bones. 



Such a combination of large tusks with rudimentary protub- 

 erances is not what we find in any known female and seems to 

 remove all reasonable doubt as to the sex of the specimen be- 

 fore us. If this be granted, the distinction of the genus from 

 Uintatherium necessarily follows. 



It is interesting to note that Elachoceras very much resembles 

 the young specimens of the Dinocerata, especially the one de- 

 scribed and figured by Professor Marsh (see his Monograph, p. 

 15, fig. 8), though even in this young skull the protuberances 

 are much more prominent than in Elachoceras. 



Another possibility is that in Elachoceras we have the missing 

 skull of Bathyopsis ; but this I consider to be extremely im- 

 probable, from the very peculiar character of the molar teeth 



