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FOSSIL REPTILIA OF THE 



It may be that the more fragile, or less robust, character of the expanded arch is 

 connected with the loss of that part of the vertebra in most of the examples of the genus 

 of which I have hitherto had cognizance. In Chelonia the sides of the neural arches of 

 the abdominal vertebrae are represented by thin vertical plates of bone. 



The excavate modification of the centrum of Bothriospondylus is more commonly met 

 with in that element of the vertebras of Fishes, as is also the character of the large propor- 

 tion of modified chondrine in its substance. In some of the large Scomberoids there is 

 a lower as well as an upper excavation on each side of the centrum. 



The bases of the parapophyses of the abdominal vertebrae of the Haddock {Gadus 

 ceglefinus) are expanded and excavated. Pallas observed that saccular productions of the 

 air-bladder were continued into, and, as it were, lined, homologous cavities at the sides of 

 the trunk vertebrae of an allied Gadoid {Gadus Navaga). 



As the lateral fossae disappear in the caudal vertebrae of Bothriospondylus one is 

 tempted to surmise that saccular processes of the lungs, which probably, as in Sauria and 

 Chelonia, lined the mid-part of the roof of the thoracic-abdominal cavity, may have been 

 prolonged into the lateral excavations of the vertebrae. But, if so, the lungs must have 

 extended far forward as well as backward, since posterior cervical or anterior dorsal 

 vertebrae show the lateral fossae, as do the sacral vertebrae. 



In certain Pterosauria {Coloborhynchus Sedgwickii, e.g.) extensions of the lungs or 

 air-cells were continued along the sides of the neck, and did penetrate lateral depressions 

 of the centrum answering to those in Bothriospondylus. 1 



B. — Bothriospondylus inagnus, Ow. Plates VIII and IX. 



That the anterior dorsal vertebra, of which a side view is given of the natural size in 

 PI. VIII, does not belong to the same species as the previously described centrum from a 

 hinder part of the trunk, may be inferred from the superior proportions of the articular 

 ends to the length of the centrum. On the supposition that the present vertebra formed 

 part of the back-bone of a larger and older individual of the same species as Bothrio- 

 spondylus elongatus it would show a degree of shortness of the centrum in proportion to 

 its breadth and depth, which is unique in my experience of the characters of centrums in 

 the same region of the vertebral column. 



A vertebra, as in PI. VII, with a terminal facet eight inches in vertical diameter, 



1 Owen, "On the Vertebral Characters of the Order Pterosauria." 'Philosophical Transactions,' 

 mdccclix, p. 114, pi. x, figs. 5, 7. 



