42 
have moveable pleurapophyses terminating freely in a point, with no hsemapophyses 
other than the costal processes of the sternum may represent. In Goura, which has six 
pairs of moveable or thoracic ribs, the second pair belong to the first of the three anchy- 
losed dorsal vertebrse : in Didunculus, which has seven pairs of thoracic ribs, the second 
pair belongs to the free dorsal immediately in advance of the anchylosed mass. Sup- 
posing Didus to have had one pair of ribs behind, and two pairs in front of those that 
directly articulate with the sternum, as the vertebra PL V. fig. 7 indicates, it would 
would have had eight pairs of thoracic ribs ; and I think this excess of one pair beyond 
the formula in Didunculus to be very probable in the large-bodied, small-winged, extinct 
Ground-dove. 
As far as the series of Dodo’s neck-vertebree under my observation exhibit such 
characters, the proportion of those with neural spines, or with hypapophyses, or both, 
is the same as in the Columbidce. In this family, as in most birds, the greater part of 
the series want both processes. The cervical parapophyses, descending to form the 
sides of the carotid canal, do not meet, coalesce, and circumscribe it in any cervical 
vertebra of Goura or Didunculus ; and not any of the vertebrse of Didus, which I have 
yet received, shows such circumscription of the hsemal canal. The majority of the 
cervicals in Didus (those, viz., that lack both neural spines and hypapophyses) are 
broader and more massive in proportion to their length than in the winged Doves. The 
third cervical in Didus has both the above processes, as in ColumbidcB : the characters 
of the axis vertebra in the same family are closely repeated in that of the Dodo. In 
the Eaptores the axis vertebra is shorter in proportion to its length, and a greater pro 
portion of the cervical vertebrse at both ends of the series have both neural spines and 
hypapophyses. 
The ribs of the Dodo are as broad, in proportion to their length, as in Doves, but are 
relatively longer in proportion to the dorsal region, encompassing a more capacious 
thoracic-abdominal cavity. The ribs of the Vulture are more expanded than in Didus, 
especially where they afford the extensive attachment to the epipleurals. But I shall 
not dwell further on the comparative characters of this part of the skeleton, as more 
decisive ones of the affinity of Didus are afforded by other parts. 
In comparing the sternum of the Dodo with that of Doves of flight, the first well- 
marked difference is in the adaptive development of the keel in the last (PL III. fig. 2, 
Didunculus), and in the provision for the concomitantly broader coracoids, the grooves for 
which meet and run into each other across the fore part of the bone in existing Colum- 
hidoe (PL XII. fig. 2, V) ; consequently the inner or upper wall of the confluent grooves 
forms a median prominence (ib. e) at the front margin of the sternum, contrasting with 
the wide notch at that part of the bone in the Dodo (PL IV. fig. 4). The next differ- 
ence, as compared with Goura and most Pigeons, is the absence of the entolateral 
processes (PL XII. fig. 3, i) in the Dodo’s sternum : but Didunculus singularly exem- 
plifies its nearer affinity to Didus by a like absence of those processes ; only the sternal 
