4G 



FOSSIL REPTILIA OF THE 



They proved to be parts of the Dimorphodon macronyx, confirmed many of the 

 observations made on previously acquired specimens, corrected others, and added almost 

 all that was required for the restoration of the skeleton of this remarkable genus and 

 species, which I have accordingly attempted in PI. XX. 



The slab of Lias with the second specimen, including the skull of DhnorjjJiodon macrovyx, 

 is of larger size, shows more of the skeleton and in a more separated and definable state 

 than in PI. XVIL Nine dorsal vertebrae, third to eleventh inclusive, in natural juxta- 

 position, with the twelfth slightly dislocated, are preserved at the ujjper part of the slab 

 (PI. XVIII, d). The summits of the neural spines («s) of most of these, and the disposition of 

 many of the preserved ribs, show that they lie mainly with the dorsal aspect downward (as the 

 specimen is figured). This explains and accords with the position of the parts of the pelvis, 

 which lie a little way behind the dorsal vertebrae. The comparatively slender ilium (ga^ss) 

 is downward ; the broad ischium (^g), and the pair of spatulate pubic bones (jj^), are turned, 

 like most of the ribs, upward, as I conclude the abdominal or ventral surface of the trunk 

 was directed as the fossil lies in the figured slab. The bones of the hind-hmb, in connection 

 with the acetabulum, are turned outward, with their iimer surface exposed. The projections 

 of the trochlear terminations of the metatarsals {i, iv, eg), show that the sole of the foot 

 is turned to view. Accordingly, we have here the bones of the left hind limb. On the 

 hypothesis that the femur and tibia are seen from the outside, which at first snggests 

 itself, they would belong to the right limb, viewed in profile. But then, the broad thin 

 plate of bone contributing to the acetabulum, would represent the ilium, and the indi- 

 cations of the pelvis below the acetabulum and head of the femur would represent ischium 

 and pubis. This interpretation, however, gives to Dimorphodon proportions of pelvic 

 bones very diflerent from those determined by Wagner in Vterodactylus Kochii^ and by 

 Quenstedt^ in Pterodadylus suevicus ; and, besides, it leaves undetermined the pair of 

 bones (g4, Pl.XVlII) which closely resemble in form and proportion the 'pubic bones' {u, u) in 

 Quenstedt's instructive plate."'^ In this plate the ilia («, s) are represented as long slender 

 bones, contributing the upper but smaller proportion of the acetabulum, and extending 

 horizontally ])eyond it both forward and backward. The pelvis, in the position in which 

 I conclude it to lie in the slab figured in PI. XVIII, might well afibrd such indications of 

 the pre- and post-acetabular productions of the ilium as are there shown at 02,02- In 

 Pterodadylus suevicus the ischium contributes the lower and major half of the 

 acetabulum {tr, loc. cit.), and expands into a broad thin plate [s, ib.), having the pro- 

 portions to that of the spatulate pubis, wdiich the bone cs bears to ci, in PI. XVIII. The 

 portion of the pelvis in the original specimen being preserved in natural connection with 



1 " Uebcr Ornithocephalus Kochii," in ' Abhandl. d. math.-phys. Klasse der Bayerisclieu Akad.,' ii, 

 4to, Muiichen, 1837. 



" ' Ueber Pterodactylus suevicus,^ &c., 4to, Tubingen, 1855. 



2 111 tbc Memoir above cited. 



