Labyrinthodon /rom Warwickshire. 523 



the species of Labyrinthodon to which it belonged, will give an idea of the propor- 

 tion of the skull included in the first-described fossil ; the length of the head as 

 compared with the breadth approximates more nearly to the proportions of that 

 of the Crocodile and Nothosaurus than to those of the ordinary Batrachian skulls : 

 among existing Batrachia, the Amphiuma, in this respect, seems to have most 

 closely resembled the present species of Labyrinthodon. 



Vertebra. — The vertebra here described (PI. XLV. figg. 5-8.) was discovered in the 

 same sandstone quarry at Coton-end as the portion of the skull and upper jaw of the 

 Labyrinthodon leptognathus , and it bears the same proportionate size to those parts as 

 exists between the vertebrae and skull of the Menopome, and between a larger verte- 

 bra from the Warwick sandstone and the jaws of the larger species of Labyrinthodon 

 next to be noticed. In the larger vertebra alluded to there is evidence of a condition 

 of the articular extremities characteristic of the lower or perennibranchiate division 

 of Batrachia among existing reptiles. From the essential resemblance which will be 

 pointed out between the jaws of the two species of Labyrinthodon, it could not be an- 

 ticipated that their vertebree would present two types of structure so different as the 

 bi-concave and concavo-convex articulations. From the figure given of the smaller 

 vertebra now under consideration*, it appeared nevertheless that one of the articular 

 surfaces of this vertebra was convex, and from the form of the articular processes 

 (for this figure is unaccompanied by any detailed description), this surface seemed 

 to be the posterior one ; I therefore wrote to Dr. Lloyd, requesting permission to 

 have the vertebra transmitted to me. It was imbedded, with the exception of the 

 surface figured in the plate quoted, in the sandstone matrix. Part of the anterior 

 articular surface of the body of the vertebra was uncovered, the opposite end of 

 the vertebra was broken ofi', and a mass of the sandstone projected from the broken 

 surface. With the assistance of Mr. Clift, sufiicient of this matrix was cleared 

 away to expose the centre and bottom of a concave surface (PL XLV. fig. 8.), to 

 all appearance similar in depth and form with that on the anterior end of the 

 bone (PI. XLV. fig. 7.) ; thus proving its correspondence in this important cha- 

 racter with the vertebra of the larger species of Labyrinthodon. The body of the 

 vertebra is subelongate and subcompressed, with a smooth exterior surface ter- 

 minating below in a sUghtly produced longitudinal median ridge. Its length is 

 nine lines, its breadth at the middle four lines ; at the articular extremity nearly 

 six lines. The articular concavity appears, as in the larger vertebra, not to have 

 begun immediately from the margin, but to have been surrounded by a flat- 

 tened circular surface ; this part, however, is much broken. The depth of the ar- 

 ticular concavity is not very great ; at least four lines of the osseous tissue must 

 have intervened at the middle of the body of the vertebra between the anterior and 

 posterior concavities ; these are much deeper and more conical in the perennibran- 

 * Geol. Trans., Second Series, vol. v. PI. XXVIII. fig. 10. 



