I 



PROFESSOR OWEN ON THE GENUS DINORNIS. 323 



entire femora, tibiae and tarso-raetatarsal bones, evidently belonging, by their proportional 

 size and exact co-adaptation of articular surfaces, to the same species of bird, has enabled 

 me to detect specific characters in the femur and tibia, by which this species, for which 

 I propose the name of Dinoniis casuarinus, clearly differs from both Dinornis struthoides 

 and Dinornis didiformis. But I may be permitted to observe, that the reference of the 

 solitary mutilated femur to the young of the Din. struthoides, which I am now enabled 

 to correct, was a mistake on the safe side : the caution which refrains from multiplying 

 specific names on incomplete evidence is less hurtful to the true progress of zoological 

 science than the opposite extreme. 



The specific characters of Din. casuarinus and its distinction from Din. dromioides, 

 with which it most nearly agrees in size, and especially in length, will be most promi- 

 nently brought out by combining the descriptions of the bones of both species. 



The femur of the Di7i. casuarinus very little exceeds that of the Diii. dromioides in 

 length, but rather more in the circumference of the shaft, and very considerably in the 

 development of the two extremities. The head is relatively larger, as PI. XXIII. of my 

 former Memoir shows : the tuberosities below the middle of the back-part of the shaft 

 are more developed : the rotular interspace between the condyles is both wider and 

 deeper : the posterior half of the internal condyle is relatively much larger. But both 

 the internal and the external longitudinal narrow ridges are more marked in Din. dro- 

 mioides than in Din. casuarinus. 



The well-marked differences between the femora of these nearly similarly- sized species 

 will be readily appreciated by comparing PI. XLVI. with PI. XXII. of Vol. iii. The spe- 

 cimen figured is rather less than other femora of the same species from the same locaUty. 



The most obvious distinction between the tibise of the Din. dromioides and Din. casua- 

 rinus, in the relation of their thickness to their length, is shown in the ' Table of Ad- 

 measurements' and in Plate XLVII. figg. 1 & 2. The tibia of the Din. dromioides (fig. 1) 

 is longer and more slender, corresponding with the character of the femur : the inter- 

 space between the ectocneniial tuberosity (k) and the procnemial crista (p) at the proximal 

 end is less than in Din. casuarinus, and the procnemial ridge continued down from the 

 crista does not so soon gain the middle of the anterior surface of the shaft, and is con- 

 tinued down the middle to the lower third before it inclines to the inner side : the ten- 

 dinous groove leading to the osseous bridge (/) in front of the distal end is shorter and 

 deeper. The orifice of the canal for the medullary artery is at the same distance from 

 the top in the tibiae of both species. The antero-posterior thickness of the shaft of the 

 tibia at its proximal third is markedly less in Din. dromioides than in Din. casuarinus. 

 The difference in the plane and aspect of the surface between the anterior and fibular 

 ridge in the Din. dromioides and Din. casuarinus is well-marked. 



The proportions of the tarso-metatarsus of Din. dromioides (PI. XLVIII. fig. 2) are, 

 as those of the femur led me to conjecture*, more slender, and the bone is relatively 



* "The femur/ 16 cannot be regarded as belonging to a young individual of the gigantic species; there 



