Cariaate Birds from Central Madagascar. 355 



The tibio-tarsus is practically identical in form with that 

 of Chenalopex cef/yptiacus . It is in the metatarsus (PI. IX. 

 fig. 3) that the likeness to Chenalopex and the difference 

 from Sarcidiornis of the present species are most marked. In 

 the former this bone is relatively long and the shaft is 

 slender in proportion to the width of the articular extremities ; 

 moreover^ the inner trochlea is less hackwardly directed than 

 is usually the case in the members of the group that are 

 good swimmers^ and, in fact, the whole bone indicates that 

 the bird is a good walker. In Sarcidiornis, on the other 

 hand, the metatarsus is relatively short, the shaft square and 

 thick in proportion to the articular ends, while the inner 

 trochlea is strongly reflected backward, the whole indicating 

 that this bird is a powerful swimmer. The fossil metatarsi 

 are almost identical with those of Chenalopex ceyyptiacus, the 

 only difference being that the extremities are a trifle narrower 

 in proportion to the length of the bone, and in some cases 

 the muscle-impressions are more strongly developed. The 

 length varies from 87 to 95 mm. ; in Sarcidiornis the length 

 is from 67 to 71 mm., in Chenalopex (egyptiacus about 85 ram. 



The numerous slight differences between the skeleton of 

 the fossil and that of Chenalopex (egyptiacus appear to be 

 sufficient to justify us in regarding it as a distinct species, 

 for which the name Chenalopex sirabensis may be adopted. 

 It is, however, possible that when further remains of the bird 

 described by Newton and Gadow as Sarcidiornis mauritianus 

 are discovered it may prove to be the same. 



There are also a number of bones of smaller Anserine 

 birds. Of these the greater number belong to Anas melleri, 

 or to a species which cannot be distinguished from it by any 

 characters in the remains preserved. These include humeri, 

 a coracoid, an ulna, and some metacarpi. The length of the 

 humeri ranges from 86 to 90 mm. ; in a recent specimen the 

 length is 88 mm. 



There are also several bones of smaller Ducks. Of these 

 a left femur seems to belong to Anas erythrorhyncha ; the 

 others cannot at present be determined, owing to the want 

 of skeletons of the recent species for comparison. 



