308 PROFESSOR OWEN ON THE GENUS DINORNIS. 



referable by its size to the Dinornis struthoides. The smaller specimen (PI. XXXIX. 

 figg. 3 — 6) was obtained by William Swainson, Esq., from the North Island, probably 

 in the vicinity of the Bay of Islands, and has belonged to a species distinct from the 

 preceding, and agreeing in size with the Dinornis dromioides. Both specimens have 

 the ferruginous tint and great weight, arising from infiltration of a salt of iron (per- 

 oxide), which characterized the specimens from the North Island described in the 

 Jormer memoir ; but the cancelli of the bone contain only a little of the dry powdery 

 alluvium of the streams into which the specimens have been washed. 



Cranium. 



The cranium referred to Dinornis struthoides agrees prettj' closely in size with the 

 same part of the skull of the Ostrich, as will be seen by reference to Plate XXXVIII., 

 in which it is figured from four points of view, of the natural size ; but it is broader in 

 proportion to its height, especially in the occipital and inter-orbital regions. It is, in 

 fact, remarkably depressed, subquadrate, with two large lateral emarginations for the 

 temporal fossas {ib. g, e), and both in size and shape it is more like the corresponding 

 part of the head of the Dodo {ib. fig. 5) than that of any existing Struthious species : 

 but the upper surface of the cranium of Dinornis is gently and equably convex above, 

 the cerebral hemispheres not raising their bony covei'ing above the level of the rest of 

 the calvarium, as in the Dodo ; and the frontal region, though more elevated than in the 

 existing Struthious birds, is less suddenly raised than in the Dodo. The length of the 

 present fossil is three inches, but half an inch at least of the anterior border of the 

 OS frontis has been broken away : its breadth across the mastoids is three inches and a 

 quarter, but the breadth across the post-orbital angles appears to have been greater. 

 The breadth between the temporal fossai, which are large and deep, is two inches five 

 lines ; its vertical diameter at the deepest part, from the upper occipital ridge to the 

 under surface of the basi-sphenoid, is one inch and a half. From the occipital region 

 the depth of the cranium gradually decreases to the anterior boundary of the cerebral 

 cavity. The great occipital foramen (fig. 1 , i") is subcircular, and seven lines in dia- 

 meter, — that of an Ostrich being five and a half lines across : its plane is vertical, and 

 the single occipital condyle {ib. i) projects freely backwards, upon a short peduncle, 

 beyond the upper margin of the foramen. No existing bird presents this peculiarity : 

 the Dinornis in this respect resembles some of the Chelonian Reptiles. The broad and 

 low occipital surface of the skull slopes forwards as it rises to join the upper surface. 

 This inclination, with the slight depth and great breadth of the occiput, and the almost 

 flat upper surface of the skull, forms the most peculiar features of the present cranium. 

 The occipital region above the foramen magnum is divided by three short obtuse vertical 

 ridges into four depressions (fig. 3, d), the two median ones being half the breadth of the 

 two lateral ones, which are deeper than usual : each depression is bounded above by a 



