332 Mr. Bryce on the Discovery of the Plesiosaurus in Ireland. 



either to the Ichthyosaurus or to the Plesiosaurus ; but knowing 

 no more of comparative anatomy than enabled me to compre- 

 hend the terms of a description, I had recourse to the me- 

 moirs published in the Geological Transactions, (vol. v. part ii., 

 and second series vol. i. parts i. and ii.) by Mr. Conybeare, 

 to whose sagacity we owe almost all our knowledge concerning 

 these singular genera*. On comparing the vertebrae with his 

 drawings and descriptions, it was evident that they belonged 

 to the Plesiosaurus. Two of them are cervical, four dorsal, 

 and one lumbar. They were recognised by being slightly 

 concave at both ends, by the proportions which obtain be- 

 tween the length of the side and the diameter of the articu- 

 lating surface, by small dimples in the lower part of the body, 

 and by a slight swelling in the middle of the circular area of 

 the end, which is largest in the dorsal, and in the lumbar does 

 not at all exist. The spinous processes are almost entirely 

 broken off; so much of them remains as barely to show the 

 course of the spinal canal. The following are the proportions 

 between the side and the diameter of the end. 



Cervical. Dorsal. Lumbar. 



2* inches side. 3 inches side. 2 inches side. 



3| inches diam. 3J inches diam. 3 inches diam. 



These proportions are sufficient to distinguish them from 

 the vertebras of the Ichthyosaurus and Crocodile. But they 

 are larger in dimensions than any which Mr. Conybeare seems 

 to have met with, and appear to agree more nearly with those 

 found in England in the Kimmeridge clay, than with those 

 found in the lias. 



I am informed by Dr. MacDonnell, that single vertebrae of 

 the same kind have been found in the lias near Same ; and in 

 the collection of William Temrent, Esq. of this town, there is 

 one which was obtained from the lias of Colin-glen, and which 

 from its dimensions appears to be an extreme caudal vertebra. 



The discovery of this genus in our lias connects that forma- 

 tion most intimately with the oolites of England and France, 

 and affords us reason to hope that when fully examined it will, 

 though imperfectly developed, amply reward the labour of 

 the inquirer, by the discovery of many singular remains, which 

 may probably, like this Plesiosaurus, supply us with new links 

 in the chain of organic being. 

 Belfast Academy, March 15, 1831. 



* For a full account of these genera, see the memoirs referred to in the 

 text ; or the volume " Fossils," by E. Pidgeon, Esq., in Cuvier's " Animal 

 Kingdom," by E. Griffith, Esq., and others. 



LII. O/i 



