1904.] Allen, Mammals from Tropical America. 63 



of the main beam, the anterior one about 50 mm. long, and the more 

 apical one about 20 mm. long. 





 O. rothschildi is much darker colored when adult than 0. 



costaricensis , and the young are less conspicuously spotted 

 with white; it is also much smaller, as stated by Mr. Thomas, 

 than either 0. costaricensis, truei, or thotnasi, as shown by a 

 comparison of the skull measurements given above with those 

 of the latter as published by Miller (Proc. Biol. Soc. Wash., 

 XIV, 1901, pp. 36, 37). Two Chiriqui skulls of females of 

 0. costaricensis, slightly younger (the last molar not functional) 

 than the two from Coiba Island of which measurements are 

 given above, considerably exceed the latter in size, being 

 about 5-7 mm. broader and 15-20 mm. longer, with pro- 

 portional increase in bulk, less frontal convexity, and larger 

 antorbital vacuities. 



ii. Odocoileus costaricensis Miller. Three skins and 

 skulls (2 adult females and one young in spotted coat), and 9 

 additional pairs of antlers, Boqueron, Oct. 9 and Dec. 4 and 15. 



As said above, 0. costaricensis is larger and paler, and the 

 young are less conspicuously spotted, than O. rothschildi. 



The nine pairs of antlers vary greatly in size and massive- 

 ness, but with two exceptions are very symmetrical in form. 

 In color they are dark reddish brown, except one pair which 

 is much lighter and was probably taken soon after the shedding 

 of the velvet. 



This series is instructive as showing the variation of the 

 antlers in size and form with age, and also the individual 

 variation. Although the antlers vary so greatly in develop- 

 ment there is very little variation in the diameter of the brain 

 cavity, which ranges in transverse width from 53 to 56 mm., 

 the youngest specimens having slightly the greatest width of 

 brain cavity. With the advance of age the walls of the skull 

 thicken, so that the breadth of the skull at the postorbital 

 constriction (between orbits and base of horn pedicles) in- 

 creases from 78 mm. in the two youngest skulls to 88 in the 

 normal adult, and to 99 in the exceptionally heavy pair 

 (No. 21566, Fig. 17 g andg')- 



