AND AYES OF NORTH AMERICA. 



171 



I 



spine, nearly over the posterior zygapophyses, and vortical to the piano of the centrum. The inferior outlino of the 

 centrum of this, as of all the other vertebrae, is concave. 



Length of centrum, 



' ' top of neural arch, 



" neural spine, 



Depth from anterior zygapophysis, 

 Width of neural spine, 



Lines. 

 3.75 



2. 

 3.2 

 1.75 

 1. 



Another fractured dorsal exhibits a broader neural spine, but its form cannot be accurately ascertained; in a 

 third its extent is nearly that of a neural arch, and it has considerable longitudinal breadth to its crest. The centrum 

 of this vertebra appears to be shorter than in the last, no doubt in harmony with its position as a rib-bearing dorsal. 



Length of centrum (No. 8), 



" below posterior zygapophysis, 

 " neural arch, 



Height of vertebra (top of spine concealed), 

 " posterior zygapophysis, 



Depth centrum at condyle, 



Length centrum (No. 15), 

 Height of vertebra, 



" to posterior zygapophysis, 



Linen. 

 a. 5 

 2. 

 3. 



«. (?+) 

 2.5 

 1.1 



3.2 



4 6 



l.G 



The anterior cotylus in this, as in all the other vertebrae, looks partly downwards. The superior anterior outline 

 of the neural spine is concave, as though the straight margin were cut away to half the depth of the spine. Whether 

 this is the natural form, or result of fracture of the matrix, is not readily ascertained; in another the full width is 

 carried four-fifths way up to the crest. 



Of what are perhaps caudal vertebrae there are profiles of six, mostly with reverses; two are very perfect. In all 

 the Inferior outline of (lie centrum it is markedly concave. No. I, flu; most characteristic, differs from the others in 

 possessing a long acuminate process, projecting at an angle of 85° witli the axis of the centrum immediately below the 

 posterior condyle; or, as the inferior part of the condyle is obscured by it, at the side of it. This may be looked upon 

 as a profile of a chevron bone, or as one of a pair of lateral central processes, such as go off anteriorly in Pterosauria, 

 Ooeciliae, and Amphiumae; or, perhaps less probably, as a posterior hypophysis. That this may be the anterior ex- 

 terior extremity, though furnished with the condyle, is rendered more probable by the presence of a. short obtuse pro- 

 cess immediately upon the column, and which cannot be other than the surspectant zygapophysis. It is, therefore, 

 quite possible that this vertebra, is opisthocoelian, as Seelcy" has pointed out the ecrvicals of Dimorphodon maeronyx 

 to lie. The neural arch stands only upon the two-thirds of the centrum, next the cotylus bearing extremity, and 

 oilers the free projection of the despectant zygapophysis appropriate to the opposite extremity of a vertebra, like itself. 

 Below this extremity of the centrum is a, keel-like zygapophysis of a right angled triangular form, the centrum being 

 the hypoihenuso. 



Length of centrum, 



' ' inferior spine, 

 Depth at cotylus without zygapophysis, 



Lines. 



3.5 



1.25 



2. 



A second and larger vertebra ( No. 2) of the same type differs in the lack of zygapophysis above the condyle, and 

 of the spine below tho same. The centrum is prolonged considerably beyond the line of the neural arch; at its oppo- 



* Annuls MagM. Nat. lllst., 18C5. 



