455 
The thickness of the leg-bones in proportion to the trunk, and of the metatarsi in 
proportion to their length, in D. crassus, D. gravis, and D. elephantopus, are unique 
in the class of Birds. They are associated with a greater breadth of the trunk, and 
especially with a greater breadth of the sternum, in proportion to its length. 
The fragmentary condition of the sternum in the series of bones of Dinornis elephan- 
¢opus first received led the articulator of the skeleton in the British Museum to restore 
that bone by a model on the type of the sternum of a less robust species at that time 
obtained (pp. 124, 196, Plate XLVIITI.). Subsequently acquired specimens (p. 254, 
Plate LXXII.) have shown this bone to present in D. elephantopus the form and 
proportions of the sternum of D. crassus (Plate CXIII.), and afford a correction of 
the error! in the first attempt at a restoration of the skeleton of D. elephantopus, as 
regards the sternum (Plate LXI. fig. 1). 
As in other forms of birds, which for some time may continue rare and scantily 
represented in collections, the few species there recognized usually offer well-marked 
differences, as in tints of plumage, proportions of bones, and even in general size; but 
as knowledge increases, forms or species showing intermediate characters are brought 
to light, and the previous differences are diminished by gradational modifications, 
which not only render the diagnosis of the genera difficult, but affect that of the 
species themselves. Under foresight of this course of knowledge, I have been led to 
refer to some kinds of Dinornis as being ‘ propagable varieties.’ 
Under present knowledge certain forms of Moa seem to be limited to the North 
Island, others to the South Island of New Zealand. The less robust and longer-legged 
forms appear to have prevailed in the North Island, the more robust and shorter-legged 
kinds in the South Island, 
But already with the advance of knowledge of the extinct Dinornithide exceptions 
come to light. 
If Moas with the character of D. gravis and D. elephantopus existed only in the 
South Island to the exclusion of other forms, and if Moas with the characters of 
D, gracilis and D. casuarinus held the same exclusive position in the North Island, the 
genetic relation of such species to food and other conditions of existence respectively 
peculiar to one or the other insular tract of land might be speculated on as a condition 
of their origin with some ground of acceptance. But, as in the case of the Geospizas 
of the Galapagos archipelago, the application of that supposed possible way of opera- 
tion of nomogony, or secondary law of the origin of species, is unavailable, and the 
hypothesis in these, as in other cases, falls to the ground, 
See cut, fig. 35, p. 419; but the more perfect sternum from which this cut was taken was mutilated at 
the postmedial border, which might originally have been bifid. 
Os 
a 
