1852.] MANTELL ON DEVONIAN REPTILE. 101 



one side , the extremities are partially extended, and the thigh-bones 

 directed forwards ; the tail is curved towards the right. 



At the first glance the fossil presents so striking a resemblance to 

 the skeleton of a small lizard, that upon a hasty inspection, I had no 

 doubt that it belonged to a lacertian reptile, and anticipated but little 

 difficulty in determining the form and relations of the original : but 

 a careful examination disclosed anatomical characters, which, if I have 

 rightly interpreted, indicate an approach to the batrachian type : the 

 results of a rigid investigation and comparison of every recognizable 

 part of the skeleton are embodied in the following description. 



Cranium. — From the outline of the mutilated skull, which can be 

 traced but imperfectly, the form of the head appears to have been 

 oblong, with a gently rounded muzzle (PI. IV. 3, 4) . The remains of the 

 vomerine and palatine bones are seen between the imprints left by the 

 lower jaw, but are too much crushed to afford any satisfactory in- 

 formation as to the original form and structure of this part of the 

 cranium. The impressions of the distal or articular portion of each 

 ramus of the lower jaw are faintly shown, as sketched in PL IV. 3, and 

 4, a, a ; but I have searched in vain for indications of the divisions 

 ojf the several parts that enter into the composition of the inferior 

 maxillary bone in reptiles ; even the outline of the anterior portion of 

 the dentary piece is not traceable. 



Teeth. — Capt. Brickenden informs me that when the fossil was 

 discovered there were several extremely minute conical teeth, having 

 a smooth polished surface ; they were displaced, but distinctly visi- 

 ble. Under a highly magnifying power two or three displaced teeth 

 are still discernible (PI. IV. 1, 1 a, 2), but their original position in 

 the jaw is not obvious. I have been unsuccessful in my attempts to 

 make out the structure of the occipital condyle. 



VertebrcB. — I cannot detect the atlas or axis ; the first vertebra 

 seen in PI. IV. 9, is probably the third or fourth cervical : the spinal 

 column from this point to the sacrum consists of. twenty-four verte- 

 brae, as in the Iguana, each bone bearing a pair of ribs. Whether 

 the bodies of the vertebrae were concavo-convex, as in the Lacertians, 

 or the reverse, as in the Salamanders *, or doubly concave, as in the 

 living Axolotl (a Batrachian that inhabits the Lakes of Mexico), I 

 cannot positively determine ; but the sparry replacements of some of 

 the intervertebral spaces appear to indicate the latter modification of 

 structure : and if these casts exhibit the normal form, the vertebrae 

 must have been deeply concave at both extremities : the length of 

 a dorsal vertebra is one-ninth of an inch. 



The vertebrae are for the most part exposed dorsally ; that is, the 

 upper part of the neural arch is deeply imprinted on the stone, in 

 PI. IV. 8 : and sparry casts of the bodies of the bones constitute a 

 portion of the spine in PI. IV. 9. 



A cast from the specimen, PL IV. 8, exhibits the form of the upper 

 part of the vertebral column, so far as it can be determined from the 



* In the Salamandridce the vertebrae are convex anteriorly and concave poste- 

 riorly : the reverse of those of Frogs and Lizards : in the Axolotl they are deeply 

 cupped at both ends. 



