LUSSIC FORMATIONS. 
75 
corpus callosum ; this characterises the Placental Mammalia. Birds differ from other 
Oviparous Vertebrates in the chalaziferous ovum. The particulars in which Birds differ 
from all Mammals and agree with Reptiles are comparatively unimportant ones of the 
skeleton. The occipital condyles (e.y.) are more completely blended or unified than in 
Cetacea. The tympanic is interposed between the mandible and the mastoid, as in 
Reptiles.^ 
Two genera of Lyencephalous Mammals retain the osteological character common to 
Birds and Reptiles of the connection of the scapula with the sternum by the intermedi- 
ation of a fully developed coracoid, and it is one of several and more important characters 
disproving any sharp definition of the higher warm-blooded Ovipara, at least, from the 
Ovo-viviparous or Implacental Mammalia. 
The scapular arch retains, in Pterosauria, its crocodilian simplicity, modified in shape 
and in the angle at which the scapula meets the coracoid adaptively for the function of 
flight in the limb suspended thereto. There is, consequently, a close similarity to the 
same elements in Birds of Flight,® but without any trace of the superadded furculum. The 
articular grooves on the sternum for the coracoids communicate or run into each other at 
the mid line. The articulation of the corresponding end of the coracoid must be as secure, 
and yet with as easy a motion, due to a well-turned synovial joint (shown first in 
Pterodactylm Woodwardi and Pt. simus),^ as in any Bird. The confluence of the 
scapula with the coracoid seems not to be constant in the order Pterosauria ; and where 
it has been found, as in Dimorphodon and Pterodactylus Fittoni, traces of the original 
suture are present, as represented in the large Neocomian Pterosauria in my Monograph 
of 1859.'" 
In some specimens of Bampliorhynchus Gemningi and in BamjjhorJiynchus longicaudus 
the scapula and coracoid seemed not to have coalesced.^ The coalescence is complete and 
constant (so far as may be inferred from two specimens) in Dimorjjhodon. 
For the analysis of the characters of the humerus in Pterosauria, I may refer to my 
Monograph, Suppl. No. Ill (1861), pp. 13 — 17, PL III. The chief seat of variety is the 
“ radial crest ” (PL XVIII, 53, h, of present Monograph). In the shape and proportions 
of this extraordinary process Binorpliodon resembles Pterodactylus more than it does 
Baniphorhynchus. In the proportions of the humerus to the bo^ly there is little diversity 
in the several species. 
The antibrachium is commonly two sevenths longer than the humerus. It consists 
1 Asa taxonomic character — whatever degree of value may be adjudged to it — this mode of connection 
of the lower jaw with the skull gains nothing by calling the tympanic ‘quadrate bone,’ or by affirming 
it to represent the ‘ incus ’ or the ‘ malleus ’ of Mammalia, whichever may happen to be the favourite 
fancy of the day. 
^ ‘Monograph,’ Suppl. No. I (18.59), p. 13. 
^ ‘Monograph,’ Suppl. No. Ill (1861), p. 12, pi. ii, figs. 7 — 12. 
* Suppl. No. I, PI. Ill, figs. 1 — 5. 
5 VoiT MEYEa, op. cit., p. 18. 
