OSTEOLOGY OF THE DODO. 71 



verge of extinction through the rapid increase of population in the small island to 

 which they are restricted. In sparsely peopled continents, such as Africa, South 

 America, and Australia, brevipennate giants may still range the deserts, pampas, and 

 unfrequented wilds. The ascertained recent advent of Man in New Zealand, New 

 Britain, Ceram, Banda, Salwattie, Mauritius, Eodriguez, significantly points to the 

 conditions under which have come to pass, in lapse of time, so strange an anomaly as a 

 bird with the specially modified instruments of flight reduced below the power of 

 exerting that mode of locomotion, yet, as a bird, retaining the conditions of the 

 respiratory and tegumentary systems of the volant class, of which it has become a 

 degenerate member. With the cessation of the chief of those conditions, viz. the 

 absence of enemies, such birds necessarily perish. 



Refraining, however, from further indulgence in an easy and seductive vein of specu- 

 lation, I would recall attention to the notable protuberance in the cranial cavity of the 

 Dodo (PI. XXIII. fig. 1, o) developed towards the upper part of the vertical tentorium, 

 contracting at its lower part into the ridge dividing the prosencephalic from the mesen- 

 cephalic chamber. In the latter are the orifices for the issue of the trigeminal nerve, the 

 larger and posterior (ib. tr) giving passage to the third and second divisions, and answering 

 to the combined foramen ovale and rotundum of mammals, and the smaller and anterior 

 foramen dismissing the first or orbital division of the fifth nerve. At the upper part of 

 the mesencephalic fossa the narrow groove for the lateral venous sinus impresses and 

 defines the back part of the tentorial protuberance, above which it bifurcates, the lower 

 branch bounding or defining the wall of the superior semicircular canal and the upper 

 part of the primitive acoustic capsule. Below this arch is an oblong cerebellar fossa (ib. n) 

 which appears to have received veins from the cranial diploe. Beneath this fossa, and 

 just behind the mesencephalic chamber, is the multiperforate internal auditory depres- 

 sion. Next behind this is the outlet for the vagal nerve and entojugular vein. Below 

 this are the small precondyloid foramina. There is a falcial ridge, low and thick, indi- 

 cating the division of the prosencephalic chamber into lateral compartments for hemi- 

 spheres ; and this ridge shows a narrow groove as for a small longitudinal sinus. A 

 transverse linear groove abruptly defines the fore part of the ridge. 



The vertically expanded anterior part of the premaxillary (ib. fig. 1, 22) has a large 

 pneumatic cavity communicating by a reticulate wall mth the cells of a cancellous struc- 

 ture, larger than those of the cranial diploe. The maxillary branch of the premaxillary 

 (ib. 22*) consists of a light open-work air-diploe, with a very thin outer case of bone. 

 The short symphysis mandibulse shows a small cavity, surrounded by more minutely can- 

 cellous structure and thicker compact walls, especially at the upper and hinder parts. 



Although some characters have been too much insisted on (e. g. the " superoccipital 

 foramen ") as exemplifying the affinity of the Dodo, the more essential characters of the 

 skull relate to its true Columbine character, while the deviations from that part of the 

 skeleton of volant Doves are explicable in the adaptive developments needed for the 



