THE MAMMALIA OF THE DEEP K1VEK BEDS. 131 



Posterior to the hyoid apparatus, but not directly connected with it, the matrix 

 contains a hollow, compressed semicylinder, or spout-shaped piece of bone (Fig. 29, 

 T. c), with exceedingly thin walls, which, strange to say, is unmistakably the ossified 

 thyroid cartilage of the larynx. The position and, still more, the shape of this bone 

 do not admit of the least doubt as to its nature, and this is one more added to the 

 many peculiarities of this very peculiar family, though whether the character is con- 

 fined to the present genus or is common to many other members of the group is not 

 luiown as yet. Obviously, only by the rarest chance could such a fragile structure 

 be preserved. Possibly the ossification of this cartilage is a sexual character, for, as 

 already mentioned, the skull with which the specimen was found associated is very 

 probably that of a male. The function of this bone was probably similar to that 

 performed by the enormously inflated basihyal of the howling monkeys, and must 

 have given to these animals most unusual powers of voice. So far as I can discover, 

 such ossification is not known elsewhere among the Mammalia. 



There is no available material to compare the hyoid apparatus here described 

 with that of the other genera of the family, since these bones are but rarely found in 

 a fossil state. One specimen of Mporeodon from Oregon shows, however, that the 

 stylohyal in this genus resembles in size and shape that of Mesoreodon. 



Measurements. 



MALE. FEMALE. 



M. M. 



Length of skull from summit of occiput to end of nose 252 .248 



Length from occipital condyles to incisive alveoli 232 .234 



Distance from summit of inion to base of lower jaw (vertical) 180 .187 



Length of cranium from summit of inion to postorbital margin 135 .133 



Length of face from postorbital margin to end of nose 126 .126 



Height of occiput 085 .078 



Breadth of the same at base 070 .070 



Breadth of skull at zygomatic arches 142 .142 



Breadth of skull at postorbital arches 110 .12 



Breadth of face at upper first premolars 040 .047 



Breadth of face at last molars 080 .085 



Length of parietal crest 098 .089 



Length of frontals in median line 050 .058 



Length of nasals in median line 100 .100 



Breadth of face between frontal angular processes 029 .033 



Vertical diameter of orbit 030 .039 



Transverse diameter 030 .030 



Height of lower jaw at coronoid process .096 



Height of lower jaw at condyle 090 



Height of lower jaw back of last molar 049 



Height of lower jaw at third premolar 031 



.053 

 .034 



