70 
FOSSIL REPTILIA OF THE 
truth of the matter can put aside the ‘post-coracoid lateral emarginations/ and other 
modifications defined in that Monograph as ‘distinctive Pterosaurian characters.’ No 
Bird has shown any approach to them. What modifications of the Pterosaurian sternum 
DimorpJiodon may have presented, we have yet to learn. 
In all cases in which it has been observed, the sternum in Pterosauria (fig. I) resem- 
bles in essential characters that of Crocodilia (fig. 2); its chief part is a longitudinal, com- 
pressed, deep bar (59), expanding laterally, some way from the fore-end, for the articulation 
of the coracoids (5l),^ and having the posterior expansion (eo), which remains cartilaginous 
in the Crocodilia, more or less ossified, in the form of a thin semicircular plate : but the 
whole bone, though adaptively modified for attachment of muscles of flight, preserves the 
characteristic shortness compared with the trunk, and offers a striking contrast to the long 
and large subabdominal plastron in most birds of flight. There is no distinct T-shaped 
episternum, such as exists in most Lacertia, and no trace of clavicles as in Lizards and 
Birds. Distinct lateral elements for articulation with sternal ribs I have not satisfactorily 
made out in any specimen. 
The abdominal haemal arches consist of slender haemapophyses and of chevron -shaped 
haemal spines. 
There is evidence of one lumbar or ribless vertebra anterior to the sacrum, in Bimor- 
pliodon ; and no Pterosaurian appears to have shown more than two such vertebrae : in this 
character we are again directed to the true Reptilian relation of Pterosauria, and warned 
oflf the beguiling marks of Avian affinity. 
The indications of epipleural appendages of ribs, more or less bony, if rightly inter- 
preted, answer to the gristly ones in Crocodilia and some Lacertia The restoration of the 
bony cage of the thoracic-abdominal cavity of Bimorpliodon (PI. XX) is based on the 
analogy of better preserved specimens of Pterosauria in regard to this part of the skeleton. 
Scattered elements of the hsemal arches, ‘ abdominal ribs,’ &c., have alone been met with 
in the specimens of Bimorphodon hitherto obtained. 
The sacrum, on the probable hypothesis of retention of the length of centrum shown 
in the lumbar vertebra, would include at least four vertebrae ; if, as by the analogy of the 
sacrum (figured in PI. II, fig. 26, of the Monograph, &c., Supplement No. I, 1859), the 
vertebrae lost length at this confluent tract, there might be five or six sacrals articulating 
with the iliac bones m Bhrmplodon. Von Meyer figures 5 — 6 anchylosed sacral vertebrae 
in his Pterodactylus duhius and the sacrum appears to consist of at least six confluent 
vertebrae in PhamphorhynclMS yrandi pelvis, Von Meyer.‘‘ 
With all the evidence that the Pterosauria, like the Binosauria and Bicynodontia, 
' ‘Monograph on Cretaceous Reptilia,’ Supplement, No. Ill (1860), PI. II, figs. 7 — 12. 
2 k% \n Hatteria, see GUnther’s excellent Memoir, in ‘ Philos. Trans.,’ Part II, 1867, p. 13, pi. ii, 
figs. 17, 24. 
® Op. cit., p. 17, pi. vi, fig. 1. 
^ Op. cit., p. 53, pi. viii, fig. 1. 
