1867.] PROF. HUXLEY ON THE CLASSIFICATION OF BIRDS. 469 



rudiment of It ; and the scapular end of each clavicle is not expanded 

 and T-shaped. 



The lower larynx has not more than one pair of intrinsic muscles. 



This group contains three very distinct families — the Trochilidce, 

 the Cypselidce, and the Caprimulgidai. 



The first two families have a length of the manus and a brevity 

 of the humerus which is peculiar to themselves, being only ap- 

 proached by the Swallows, and in a less degree by the Gaprinmlgidce. 

 In both CaprimuJgus and jEgotheles the manus is slightly longer 

 than the ulna, and the latter considerably exceeds the humerus in 

 length. 



Both the Swifts and the Goatsuckers have a slight rudiment of a 

 vertical process develo|)ed from the middle of the furcula. JEgo- 

 theles a[)proaches the Swifts more nearly than Caprimulgus does in 

 the form of its palatine bones, and in the absence of basipterygoid 

 processes. 



The Cypselidoi are very closely related to the Swallows among 

 the Coracomorphae, while the CaprimuIgidtB come near Trogon, and 

 more remotely approach Podargus and the Owls. 



The CORACOMORPH^.. 



There are no basipterygoid processes. 



The vomer, single in the adult, is truncated in front and deeply 

 cleft behind*. The maxillo-palatines are sometimes slender and 

 rod-like, sometimes broader, but are never concavo-convex lamellae, 

 or tumid and elongated as in most Schizognathae. The postero- 

 external angles of the palatines are always well marked, and are fre- 

 quently produced backwards. 



The sternum has a forked manubrium, a strong carina with an 

 excavated anterior edge, long costal processes, and, except in one or 

 two cases {Pferoptochiis and Scytalopus), its posterior edge has a 

 single notch on each side. 



The clavicles have expanded T-shaped scapular ends, and send back 

 a vertical process from their inferior junction (except in Menura). 



There is a conical scapula accessoria. 



The tarso-metatarsus has a tuberosity perforated by six distinct 

 canals for the flexor tendons. 



The pollex is strong and turned backwards. 



The basal phalanges are not longer than the penultimate, but 

 usually much shorter in the anterior toes. 



The contour-feathers have a small aftershaft, and the oil-gland 

 has no circlet of feathers. 



There is only one carotid, the left. 



The lower larynx presents every degree of complexity. It may 

 be wholly tracheal, or, as is more commoidy the case, partly tracheal 

 and partly bronchial ; it may be devoid of muscles, or may have six 

 pairs, or may be enveloped in a muscular mass. 



* Nitzsch (Art. Passerinae, Ersch unri Griilier's ' Encyclopaedie,' 1840) was the 

 first to indicate this and many other distinctive characters of this group. 



