1909.] OF MONKEYS OF THE GENUS PITHECIA. 933 



been mentioned, since the late Prof. Weldon observed (14) in a 

 female monkey of the genus Callithrix not only that the thyroid 

 cartilage was swollen but that there vras a patch of ossification on 

 each side, which facts '• seem to show the possible existence of a 

 howling apparatus in the male." 



It is obvious, however, from Weldon"s figure of the larynx of 

 Callithrix gicjot (14, p. 9, fig. 4), that the thyroid cartilage, if 

 " swollen," is relatively small to the rest of the cartilage and bones 

 in the neighbourhood, when compared with PitJiecia. So large 

 and swollen is this cartilage in Fithecia jnthecia that there is 

 hardly any thyroid notch along the upper ventral border where 

 the cartilage is in contact with the body of the hyoid, nor is thei-e 

 any marked " Adam's apple."' The whole surface of the cartilage 

 ventrally is uniformly convex. The proportion between the 

 thyroid and cricoid pieces of the larynx and the body of the 

 hyoid are to be seen in the figure of the isolated larynx seen 

 from the ventral aspect (text-fig. 288). Although the thyroid 



Text-fig. 289. 



Cn 



Hyotd and lar^-nx of Fithecia fithecia viewed laterally. 

 Cr. Cricoid cartilage. Other letters as in text-fig. 288. 



cartilage is smooth and almost bubble-like Avhen viewed from the 

 ventral aspect, it is flattened and ridged laterally where the thyro- 

 hyoid nuiscle is attached. As in Callithrix (cf. Weldon), the an- 

 terior and posterior coi-nua of the thyroid cartilage are not very 

 pronounced. The posterior cornu is the most conspicuous. So far 

 it is clear that Pithecia resembles Callithrix more nearly than it 

 does Mjjcetes* . The ciicoid is ossified in the middle line ventrally, 

 which fact is indicated by dots in the accompanying figures (text- 

 figs. 288 & 289) of the larynx of Pithecia pithecia. The lateral 

 regions of the cricoid are not ossified. The lateral view of the 

 laryngeal cartilages (text-fig. 289) may be compared with Weldon's 

 figure of the same cartilages in Callithrix^ when the diflerences 

 in their proportions will be very apparent. The hyoid bones are 

 correctly figured in the same drawings. The anterior cornu is 

 cartilaginous. The tracheal rings present only one feature worthy 



* The larynx, &c. of this genus is figured by Wiedersheim iu the 1886 edition of 

 the Vergleich. Anat. der Wirbelthiere, p. 641. 



63* 



