ON THEC0SP0NDYLU8 DAVIESI. 79 



9. On THECOSPONDrLTJs Davtesi (Seelei/), with some Eemarks on 

 the Classification of the Dinosatjria. By H. G. Seeley, 

 F.R.S., F.G.S., Professor of Geography in King's College, 

 London. (Read December 7, 1887.) 



In the Fox Collection in the British Museum is the anterior third 



El 

 of a vertebra, with the number ^p from the Wealden Beds of Brook, 



in the Isle of Wight, which indicates an animal of a type which 

 hitherto has had but one other representative in Europe. With 

 his usual acumen Mr. William Davies, F.G.S., recognized it as 

 being the cervical vertebra of an animal closely allied to the genus 

 Goelurus of Marsh, ^o one would have been more competent than 

 that veteran palaeontologist to have written its history ; and if I 

 gladly undertake the task, it is because it enables me to suggest this 

 honour to the work of a distinguished pioneer, whose labours on 

 the Fossil Yertebrata have smoothed the way and facilitated the 

 studies of every student of the National Collections for the last 

 quarter of a century. 



Imperfect as the specimen is, it may serve as a nucleus round 

 which knowledge will accumulate, until the genus becomes as well 

 known as the larger Wealden reptiles. 



The centrum is elongated, compressed from side to side, with a 

 flattened base, and flattened subquadrate anterior articular face, with 

 the sides of the face prolonged backwards as subparallel sides, and 

 as a ventral surface which is subparallel to the neural canal. The 

 cervical ribs are co-ossified with the centrum and neural arch. The 

 bony tissue, not unlike that of Ornithosaurs for its relative thick- 

 ness, forms a dense external film, which defines the form of the bone, 

 and is connected with some delicate internal supports in the cham- 

 bered neural arch ; so that there is no solid tissue in neural arch or 

 centrum, and the densest layer is the film around the large neural 

 canal. The neural arch forms a long pent-house ridge, which is 

 penetrated in front above the neural canal by a large subtriangular 

 cavity. 



The only European genus hitherto described in which the ver- 

 tebrae are similarly elongated, compressed from side to side, and 

 enveloped in a dense external film of bone, is that indicated by the 

 sacrum named Thecospondylus Horneri. The internal mould of that 

 specimen, and the fragmentary vertebra of this, are confessedly 

 scanty materials for comparison; but as they agree in characters 

 which define them from all other animals, I believe it will be legiti- 

 mate to refer both to the same genus, though there is the possibility 

 of their belonging to distinct genera which are nearly allied. In the 

 type of Thecospondylus Horneri the sacral vertebrae are about 11 centi- 

 metres long, andlestimate the vertebra about to be described as having 

 been 9 centims. long, so there is no great difi'erence in size. But 

 since Thecospondylus Horneri has the sacral vertebrae convex trans- 



