248 PROFESSOR OWEN ON THE GENUS DINORNIS. 



The shaft is rounded, not compressed and subtriedral as in the Ostrich : in no bird are 

 the muscular ridges and tuberosities so strongly developed on the posterior part of the 

 shaft : the orifice of the medullary artery is at the middle of this surface. The popli- 

 teal space is deeply excavated. There is a rough deep oval depression at the upper 

 and back part of the outer condyle. In only one out of eighteen femora are the pa- 

 rietes of the bone deficient at the part where the air is admitted into the interior of 

 the shaft in the Ostrich, Emeu, Rhea, and Cassowary ; but in the exceptional instance 

 cited (PI. XXIX. fig. 1.) the cavity h does not lead to the interior of the bone, and may 

 be due to accidental fracture, as there is a similar opening on the opposite side. In all 

 the other femora of the Dinornis the parietes at the back part of the proximal extremity 

 of the bone are entire, as in the Apteryx ; and both the weight and cancellous structure 

 of these bones prove the accuracy of the statement made in the description of the ori- 

 ginal fragment, that the Dinornis retains the medullary contents of the cavities of the 

 femur throughout life, as in the Apteryx, which is the only other known example of a 

 terrestrial bird in which the air is not admitted into any of the bones of the ex- 

 tremities. 



The absence of the air-hole and air-canal, the great thickness of the dense bony wall 

 of the medullary cavity of the shaft', the tuberosities on the back part of the shaft, the 

 great size of the distal end of the femur, and especially the great breadth of the rotular 

 cavity, constitute the chief generic characters of this bone in the Dinornis. 



Dimensions of the Femora. 



Femur. /I. /2. /3. /12. /13. /6. /16. /8. /7. /17. /lO. 



In. Lin. In. Lin. In. Lin. In. Lin. In. Lin. In. Lin. In. Lin. In. Lin. In. Lin. In. Lin. In. Lin. 

 Length 16^? 13 00 110 96 94 96 8 80 81 00 



Breadth of proximal end l 



,. , .^ , , ,.^00 4 10 00 42 35 36 36 2 10 30 33 00 



(in the axis oi the neck) J 



Breadth (transverse) of ) 

 ^. ,\ ' ^00 52 00 43 39 37 37 33 32 36 00 

 distal end J 



Circumference of middle .73 61 60 56 51 41 43 40 40 43 21 



Of the eighteen femora transmitted to England, eleven of which are more or less 

 complete, and the dimensions of most given in the subjoined table, there is a more 

 regular gradation of size than in the tibiae and metatarsi ; and, as the table demonstrates, 

 a greater correspondence in their general proportions. 



Nevertheless it is obvious that there is a similarity of size in a certain number, which, 

 if the maturity of the bones be granted, must therefore indicate particular species. 

 Thus, whether we glance at the series of the bones themselves, or on the table of ad- 

 measurements, we have no hesitation in grouping together/6,/ 16, the length of which 

 ranges between 9j inches and 9^ inches : / 13, though similar in length, is obviously a 



> Compare fig. 1 with fig. 2 in PI. XXIX. 



' According to the obvious proportions of the articular extremities if entire. 



