LIASSIC FORMATIONS. 



49 



In tlic left ramus of the maiulible two of the large anterior laniarics are in place ; one, 

 answering to the second in PI. XVil, 2', })rojects across the diastema between the second 

 and third tooth above ; in size, shape, and curvature, it resembles the second upper laniaiy, 

 close to which it terminates. The next mandibular tooth is larger, less curved, and crosses 

 the middle of the interval between the third and fourth upper laniaries. The tooth (!') 

 displaced beneath the mutilated fore part of the mandible, I take to be the foremost of 

 the mandibular series and suppose that its point would naturally project across the interval 

 between the first and second of the upper teeth. The fourth laniary appears to be more 

 displaced : its base or root, with a lateral depression, is shown behind the fifth tooth of 

 the minute serial teeth, and the crown passes obliquely backward on the inner side of 

 that of the sixth upper laniary, by which it is concealed. Of the serial teeth, with pointed 

 crowns from half a line to a line in length, about thirty may be reckoned occuj)ying an 

 alveolar extent of 2 inches, 9 lines. 



At the hind j)art of the left mandibular ramus, here exposed, three longitudinal 

 ridges define two vacuities, of which the inferior may be natural. The upper one seems 

 more plainly due to loss of the thin outer plate of bone extended between the upper two 

 ridges. The proportions of the ramus closely accord with those of the first-described 

 specimen. The fore part of the mandible is too much mutilated for useful comparison. 



The dentition of Dimorphodon, as displayed by the second specimen of skull, consists, 

 in the upper jaw, of laniaries with wide intervals, eleven in number on each side ; in the 

 lower jaw, of foiu*, if not five, laniaries implanted at the fore part of each ramus of the 

 mandible at intervals corresponding with three of the four anterior laniaries above ; then 

 follows the long series of close- set and minute pointed teeth. The difference of dentition 

 as compared with the first specimen (PI. XVII) is, in the upper jaw, in the additional 

 small laniary or cuspidate tooth at the back part of the series in that specimen. In the 

 lower jaw there does not seem to be any noteworthy difference in the number, kinds, and 

 position of the teeth. The longest laniaries are included between the second and fifth in 

 both jaws : the upper laniaries after the fourth become small and straight. 



At the first view of the framework of the huge head of our Liassic dragon one is 

 struck with the economy of bony material and the purposive skill with which it has 

 been applied or disposed, so as to give strength where resisting power was most required. 



The lodgment of the poorly developed brain enlists a miserably small proportion of the 

 skull : the cranium proper, or brain-case, is relegated to an out-of-the-way corner, so to 

 speak, and there it is almost concealed by the projections for joints or muscular 

 attachments. The orbits accord with the large eyes given to this volant and swift-moving 

 Reptile. 



One can conceive no necessary interdependent relation between the wide external 

 bony nostril («) and the organ of smell, nor be led to conjecture that the tegumentary 

 inlets to the nasal chamber Avere (larger than is usual in Reptiles. 



The main purpose of the head is for prehension of i)rey. The jaws are produced far 

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