400 Dr. J. jMurie on the Mutmots and their Affinities. 



Concerning the yoke-footed and ^-toed Bucerotidse, as Alph. 

 Milne-Edwards observes ^ : — " II est imjDOSsible de confondre 

 le tarso-metatarsien des Calaos avee celui d^aucun autre oiseau ; 

 cet OS est tres-enfle et remarquable par ^existence de deux 

 pertuis superieurs enormes qui servent en meme temps de trous 

 pneumatiques." Their sternum has but one pair of xiphoid 

 notches ; and in a variety of ways their skull is vastly different 

 from that of the Motmot^s. 



The foot of the Trogonidse is ^-toed ; the first and second are 

 those thrust behind. The upper extremity of the tarsus has a 

 most unusual elongate posterior process, and two perforations 

 at the side ; the lower end of the same bone has an enlarged ex- 

 ternal knuckle (trochlea), and the internal one thrust backwards. 

 The pelvis is short and broad to an extreme^ the ischium long. 

 There is an interclavicle (at least in Trogon mexicanus and T. 

 atricollis) ; and the coracoids meet inferiorly. The skull is broad 

 and short, more Swift-like than that of the Motmots. There is 

 a considerable interorbital space. Maxillo-palatines reduced to 

 narrowed extending plates. An extensive palatal and postnarial 

 cleft, and the palate-plates narrower. Basipterygoid processes 

 obtain. All these are most important and trenchant distinctions 

 from the Momotidse. 



The skull of the Jacamars^ judged by Galbula leucogastra 

 (the broader-billed section, Jacamerops, &c., not having come 

 under my observation), has a very different form from that of the 

 Motmot^s. There is attenuation of the beak, a short lofty brain- 

 division, descent of the postfrontal process to the jugal, &c. 

 Their sternum, with part likeness to Todus, has great fissures and 

 delicate rods. Their tarsus and the zygodactyle construction of 

 the foot also exclude their close relation to the Motmots, advo- 

 cated by some. 



• Lastly, as to the Raraphastidse, Toucans. Their zygodactyle 

 foot coordinate with adaptive alteration of the lower end of 

 the tarsus, peculiar enlargement of the bottom of the femur, 

 pelvic elongation, foi-ward lengthening of sternal keel^ division 

 of the clavicles (united in Pteroglossus) , and upper enlargement 



* * Reclierclies sur les Osseaux Fossiles de la France,' tome ii. p. 305, 

 and Atlas, ii. pi. clxix. figs 24, '2o. 



