330 Geological Society. 



transverse, oblique and spinous processes broken off, equalled in di- 

 mensions a middle caudal vertebra of a full-sized whale, the antero- 

 posterior diameter being five inches, the transverse eight inches six 

 lines, and the vertical seven inches. The sides and under part of 

 the centrum are described as very concave ; and the shape of the 

 articular extremities as nearly circular, with a greater concavity in 

 the anterior one than in the posterior. The posterior hsemapophysial 

 articular surfaces slope downwards and forwards in the form of semi- 

 circular facets for nearly two inches upon the under surfaces. The 

 neurapophyses commence close to the anterior surface of the cen- 

 trum, their antero-posterior extent being three and a half inches, 

 and they meet at a rather acute angle above the spinal canal. The 

 vertical diameter of the spinal canal was one inch nine lines, the 

 transverse t^\-o inches, and the breadth of the base of the neural arch, 

 from the outside of the neurapophyses, five inches three lines. The 

 transverse process is developed from the centrum just below the neu- 

 rapophysial suture. In all the caudal vertebras of the Cetiosaurus 

 the posterior half of the centrum is left uncovered by the neural 

 arch. 



The substance of another fractured vertebra, showing the upper 

 third of the centrum, presented an uniform coarse spongy texture ; 

 whilst in a third specimen, which exhibited also a similar texture, 

 the layers affected a direction parallel with the articular extremities 

 for about half an inch from their surfaces, and inclined to the longi- 

 tudinal course in the intermediate space. This structure, Mr. Owen 

 states, proves that the vertebra cannot belong to the Poikilopleuron 

 Bucklandi. 



A caudal vertebra also from Buckingham, and assigned by Pro- 

 fessor Owen to the middle part of the tail, on account of the de- 

 velopment of short, narrow transverse processes just below the 

 neurapophysial sutures, exhibited a centrum of a subtrihedral form, 

 with one angle inferiorly and the other two at the origin of the 

 transverse processes, but all three largely rounded off. The marginal 

 circumference of the centrum was convex, and separated from the 

 lateral or free surface by a rough, irregular, elevated ridge, the in- 

 ferior part of which encroached upon the under surface of the ver- 

 tebra in the form of two semicircular facets, both anteriorly and 

 posteriorly. The free surface of the vertebral centre is marked by 

 the coarse lines of the bony fibrous structure, decussating like an 

 irregular net- work. The spinal canal of this specimen did not sink 

 into the body of the vertebra. The size of this vertebra, and the 

 proportions and position of neurapophyses and haemapophysial arti- 

 culations, might suggest a relationship of the animal to which it 

 belonged with the Cetacea ; but it differs, Mr. Owen says, in the 

 concavity of the terminal articulations, which show no sign of sepa- 

 ration as laminar epiphyses, and more particularly in the place of 

 the origin of the transverse process being close to the neurapophysis 

 instead of proceeding from the middle of the side of the centrum. 

 In these deviations from the Cetacea, the Cetiosaurus apjiroaches, 

 the author states, the saurian order. 



