MUSOPHAGI 



alliance between Musophagidse and Cuculidte it may be 

 useful to tabulate the principal divergences in the skull. 



Corythaixh&s~L4: cervical vertebra' ; ' the <tt1x is notched, 

 not perforated by the odontoid process. Four ribs reach 

 the sternnm, which is doubly notched and has a strong 

 spina externa. 



In the pelvis the prepubic process is very markedly 

 developed, as in Geococcyx. 



The clavicle comes into contact both w r ith the scapula 

 and with the moderately large procoracoid ; the latter is 

 fused with the acrocoracoid, 2 making thus a complete bridge 

 over the sulcus supracoracoideus. The coracoids slightly 

 overlap at their articulation with the sternum. 



The heemapophyses are characteristic. In Corytlia ix albo- 

 cristata Cll has paired processes ; on C12 and C13 the hsema- 

 pophyses form a continuous ventral keel to those vertebrae. 

 The three following vertebrae have hsemapophyses. The 

 extremities of those of Dl and D2 are expanded with a 

 median ridge, ow T ing to the catapophyses having descended 

 them. 3 



OPISTHOCOMI 



Definition. Aftershaft present. Oil gland feathered. Rectrices, ten. 

 Q/uintocubital Muscle forrrmla, ABX~S~ + . Biceps slip and 

 expansor secundariorum present. Carotids, two. Caeca present. 

 Skull holorhinal, schizognathous, without basipterygoid pro- 

 cesses. Sternum peculiar in form, wider behind than in front ; 

 the spina externa ankylosed with furcula. 



Tjiere is no doubt that this group, consisting of but 

 a single genus and species, Opistliocomus cristtus, the 

 hoatzin of British Guiana, forms a well-marked group of 

 birds. 



The external characters of the adult and young have been 

 chiefly described in recent years by NITZSCH, PYCBAFT, 4 and 



1 In Corythaix persa the atlas ring is incomplete. 



2 Cf. Galli, in which the same fusion occurs. 



3 E. BLAKCHARD, ' Remarques sur 1'Osteologie des Musophagides,' 

 Rend. xlv. p. 50!). 



4 ' On the. Pterylography of the Hoatzin,' Ibis, 1895, p. 345. 



