44 



E. M. MUSEUM MEMOIRS. 



presence of the long canine tusks are features seldom found in animals provided 

 with horns. It is more likely that they gave support to masses of callous 

 epidermis. However covered they gave the animal a very formidable appear- 

 ance. 



There are many evidences that may be derived from the study of the skulls 

 of the wide variations in form and size which this remarkable genus attained. 

 The median protuberances in the L. Speirianum skull figured measure about six 

 inches from the tip to the inner side, and three and a half inches in the fore-and- 

 aft diameter at their bases. Of the same shape is a corresponding protuberance 

 which has been broken from the skull to which it belonged. It is only three and 

 a half inches long, with a transverse diameter of two inches. Showing the enor- 

 mous size which these animals sometimes attained, we have the forward portion 

 of a skull bearing protuberances which measure nine inches from base to tip, 

 found in the Loxolophodon beds. If these were in the same proportion as those 

 borne upon L. cornutus or L. Speirianum, they would indicate a head over four 

 feet long. From present data it is of course difficult to form any conjecture re- 

 garding the influences of age and sex upon the strange outlines of these skulls, 

 and there is little doubt that purely sexual or immature characters have been 

 employed in fixing species and perhaps genera. Evidence is, however, wanting 

 that the sexes varied in their dentition, as no exceptions to the dental formula 

 given above have, as far as is known, appeared. 



General conclusions. In the upper Cretaceous or early Eocene, lived a group 

 of animals which were the common ancestors of the Dinocerata and Pantodonta 

 With the Dinocerata arose on a common branch the ancestors of the Proboscidia, 

 the two groups remaining united for some time, and then separating. The Dino- 

 cerata branched off as an aberrant group, gradually losing the characters of the 

 main stem, and, as far as we know, becoming extinct at the close of the Eocene. 

 They are related to the Proboscidia in numerous points of structure which are 

 detailed in the preceding pages. On the other hand, it follows from their com- 

 mon origin that the Dinocerata are related to the Perissodactyle Ungulates 

 through Coryphodon, presenting several points of likeness with Rhinoceros. 

 These resemblances are also pointed out in this memoir. 



