xr " HOWLING " OF MESOREODON 3 3 I 



thyroid cartilage of the larynx was found. As the skull was 

 that of a male, this character may he a sexual one. It is quite 

 comparable to the ossification of the same cartilage in the 

 American monkey Callithrix. " Tlie function of the bone," 

 observes Professor Scott,^ " was probably similar to that per- 

 formed by the enormously -inilated basihyal of the howling- 

 monkeys, and must have given to these animals most unusual 

 powers of voice." Another important anatomical fact aljout 

 Mesoreodon is the apparent existence of a clavicle. It is of 

 course conceivable that the remains of some other animal have 

 got mixed up with that of the individuals upon which the 

 present genus is founded ; but failing that, here is a clavicle in 

 an Ungulate. The spine of the scapula possesses a metacromio^. 

 This greater development of the spine of the scapula in Artio- 

 dactyles than in Perissodactyles is, it is svTggested, to be cor- 

 related with tlie earlier loss of the clavicle in the latter group of 

 Ungulates. 



Cyclo^ndiiis (synonymous witli Bracliymeryx^ is a kind of pug- 

 form of Oreodon. The skull is short and l)road, and the end of 

 the snout a little turned up. The upper incisors are small and 

 drop out early. On each side of the nasals is a large oval 

 vacuity which is perhaps to be compared to the lateral deficiency 

 to be found in other .Vrtiodactyles. One species of this singular- 

 looking form is appropriately called C. simus. 



Other allied genera are Mcryclbyas and Leptauchema. The 

 former extends as far down as the Lower Pliocene, and is thus 

 one of the newest forms of Oreodontidae. 



A(/riocJwerus'-' (Pig. 178) is placed in a separate sub-family from 

 the types which have just been considered. It is Miocene in range. 

 It differs from Oreodon and its closer relatives by the fact that the 

 orbit is open behind and not closed. The most remarkalile fact 

 about this creature is that the terminal phalanges of the digits 

 (five in the fore- and four in the hind-feet) l;)eing pointed, seem 

 to suggest their encasement with claws rather than hoofs. The 

 pollex, though small, seems to have been opposable. As with 

 other Oreodonts, the molars are selenodont. The premaxillae 

 are toothless — at least in adults, for two teeth are present in the 



^ Trans. American Plvil. Soc. xviii. 1S96, ]>. 125. 



^ For complete osteology see Wortnian, Bull. Amer. Mus. Nat. Hist. vii. 1895, 

 p. 145. 



