XI “HOWLING” OF MESOREODON Ben 
thyroid cartilage of the larynx was found. As the skull was 
that of a male, this character may be a sexual one. It is quite 
comparable to the ossification of the same cartilage in the 
American monkey Callithriz. “The function of the bone,’ 
observes Professor Scott,’ “was probably similar to that per- 
formed by the enormously-inflated basihyal of the howling 
monkeys, and must have given to these animals most unusual 
powers of voice.” Another important anatomical fact about 
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 metacromion. 
This greater development of the spine of the scapula in Artio- 
dactyles than in Perissodactyles 1s, 1t 1s suggested, to be cor- 
related with the earlier loss of the clavicle in the latter group of 
Ungulates. 
Cyclopidius (synonymous with Brachymeryx) is a kind of pug 
form of Oreodon. The skull is short and broad, 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 
racuity which is perhaps to be compared to the lateral deficiency 
to be found in other Artiodactyles. One species of this singular- 
looking form is appropriately called C. simus. 
Other allied genera are Merychyus and Leptauchenia. The 
former extends as far down as the Lower Pliocene, and is thus 
one of the newest forms of Oreodontidae. 
Agriochoerus” (Fig. 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 1s open behind and not closed. The most remarkable fact 
about this creature is that the terminal phalanges of the digits 
(five in the fore- and four in the hind-feet) being 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 Phil. Soc. xviii. 1896, p. 125. 
* For complete osteology see Wortman, Bull. Amer. Mus. Nat. Hist. vii. 1895, 
p- 145. 
