146 REPORT — 1841. 



For the opportunity of examining the rare and interesting remains of the 

 Rhynchosaurus I am indebted to Dr. Ogier Ward of Shrewsburj^, and to the 

 Council of the Natural History Society of that town, in the museum of which 

 many of the fossils here described are deposited. 



They occur at the Grinsill quarries, in a fine-grained sandstone, and also in 

 a coarse burr-sandstone ; in the latter are imbedded some vertebree, portions 

 of the lower jaw, a nearly entire skull, fragments of the pelvis and of two 

 femora: in the fine-grained sandstone, vertebrae, ribs, and some bones of the 

 scapular and pelvic arches are imbedded. The bones present a very brittle 

 and compact texture ; the exposed surface is usually smooth, or very finely 

 striated, and of a light blue colour. The sandstones containing these bones 

 occasionally exhibit impressions of footsteps which resemble those figured in 

 the Memoir by Messrs. Murchison and Strickland, Geol. Trans., 2nd Series, 

 vol. V. pi. xxviii. fig. 1, but differ in the more distinct marks of the claws, the 

 less distinct impression of a web, the more diminutive size of the innermost toe, 

 and an impression corresponding with the hinder part of the foot, which Dr. 

 Ward compares to " a hind-toe pointing backwardt-, that, like the hind-claw 

 of some birds, only touched the ground with its point, which was armed in 

 some of the foot-prints with a claw still longer than those of the fore-toes *." 

 The foot-prints are likewise more equal in size and likewise in their intervals 

 than those figured by Messrs. Murchison and Strickland : they measure from 

 the extremity of the outermost or fifth toe to that of the innermost or first 

 rudimental toe, about one inch and a half. They are the only foot-prints that 

 have as yet been detected in the new red sandstone quarries at Grinsill. 

 , I proceed now to describe the fossil bones, respecting which Dr. Ward ob- 

 serves, " as they have always been found nearly in the same bed as that im- 

 pressed by the footsteps above described, I am induced to believe that these 

 are the bones of the same animal :" an opinion, Avhich, from the correspond- 

 ence between the bones and the foot-prints in size, is, at least, highly probable. 



Vertebrce. — Both surfaces of the centrum are concave, and are deeper than 

 in the biconcave vertebree of the extinct Crocodilians ; the texture of the cen- 

 trum is compact throughout. The two lateral surfaces join the under surface 

 at a nearly right angle, the transverse section presenting a subquadrate form, 

 with the angles rounded off: the under surface and sides are regularly con- 

 cave longitudinally. 



The neural arch is anchylosed with the centrum, without trace of suture, as in 

 most lizards : it immediately expands and sends outwards from each angle of its 

 base a broad triangular process with a flat articular surface ; the two anterior 

 surfaces look directly upwards, the posterior ones downwards ; the latter are 

 continued backwards beyond the posterior extremity of the centrum; the tu- 

 bercle for the simple articulation of the rib is situated immediately beneath the 

 anterior oblique process. So far the vertebrae of the Rhynchosaurus, always 

 excepting their biconcave structure, resemble the vertebrae of most recent li- 

 zards. In the modification next to be noticed, they show one of the verte- 

 bral characters of the Dinosauria. A broad obtuse ridge rises from the upper 

 convex surface of the posterior articular process and arches forwards along 

 the neural arch above the anterior articular process, and gradually subsides 

 anterior to its base : the upper part of this arched angular ridge forms, Avith 

 that of the opposite side, a platform, from the middle line of which the spi- 

 nous process is developed. This structure is not present in existing lizards; 

 the sides of the neural arch in their vertebrae immediately converge from the 

 articular processes to the base of the spine, without the intervention of an 

 angular ridge formed by the side of a raised platform. The base of the spinous 

 * Extract of a letter, dated Shrewsbury, November 27th, 1840. 



