76 REPORT — 1841. 



Monheim Teleosaur*, in having the upper temporal fossae longer in propor- 

 tion to their breadth ; but it differs from the Teleosaurs of both Caen and 

 Monheim in the more equal size of the teeth, and from the Monheim species 

 in the greater number of teeth, the Teleosaurus prisons having at most 

 2g_2() = 106. The median frontal in the Wliitby Teleosaur is slightly con- 

 cave : in the Caen species it is flat. Tlie basi-occipital is perforated by the 

 common terminal canal of the Eustachian tube close to the junction with the 

 sphenoid, and, on eacli side of the hole, it expands into a rough tuberosity. 

 The body of the sphenoid is compressed, characterized by tM'o processes or 

 narrow ridges, continued one from each side of the middle of the sphenoid 

 obliquely backwards. The pterygoid bones are relatively smaller than in the 

 Gavial. The palatine bones are more extended posteriorly, and articulate 

 with the transverse bones. The posterior apertures of the nasal canals are 

 placed more forwards upon the base of the skull than in existing Crocodiles. 



Vertebral Column. — The number of vertebraj in the true Crocodiles of the 

 present period rarely exceeds sixty, which is the number originally assigned 

 by iElian-j- to the spinal column of the Crocodile of the Nile. Cuvier gene- 

 rally found 7 cervical, 12 dorsal, 5 lumbar, 2 sacral, and 34 caudal vertebraj. 



In the Crocodilus acutits a thirteenth pair of ribs is occasionally developed, 

 and, according to Plumier, it has two additional caudal vertebrae. 



The Alligator (^Alligator Lticius) has sixty-eight vertebrae, the additional 

 ones being in the caudal region. 



The Gavial has sixty-seven vertebrae, disposed as follows: — 7 cervical, 13 

 dorsal, 4 lumbar, 2 sacral, and 41 caudal vertebrae. 



The very perfect specimen in the Whitby Museum displays the number 

 of the vertebrae through the whole spinal column, and establishes another 

 difference between the Teleosaur and the Gavial, the former having a num- 

 ber of vertebra intermediate between the Crocodiles and Gavials, viz. 64, 

 with a special peculiarity in the excess of costal vertebrae, as the following 

 formula indicates, viz. 7 cervical, 16 dorsal, 3 lumbar, 2 sacral, 36 caudal. 



In all sub-genera of existing Crocodiles, as in the extinct tertiary species, 

 the hind surface of the vertebra is convex, the fore surface concave, except 

 in the atlas and the two sacral vertebrae. 



Cuvier, wlio had the opportunity of seeing only the annular part (neura- 

 pophyses) of the cervical vertebrae of the Caen Teleosaur, regrets his in- 

 ability to state Avhether either of the articular extremities of the centrum 

 were convex, or which of them %. The Whitby Teleosaur decides this ques- 

 tion, and shows that both articular extremities of the vertebrae are slightly 

 concave in the cervical as in the rest of the vertebral series. 



The atlas in the Teleosaur corresponds essentially with that of the Croco- 

 diles, as is shown by the three main component parts of this bone, from a 

 Whitby Teleosaur in Lord Enniskillen's collection. The body or centrum 

 is a transverse quadrilateral piece, smooth and convex below, narrowing like 

 an inverted wedge above, with six articular facets, viz. a concavity in front 

 for the occipital condyle, a flat rougher surface on each side of the upper 

 parte for the attachment of the neurapophyses ; a posterior facet for the an- 

 terior part of the detached odontoid element of the axis ; and the small sur- 

 face on each lateral, posterior and inferior angle for the atlantal ribs. The 

 neurapophyses are pyramidal processes, with their apices curved towards 

 each other ; they are relatively smaller in proportion to the centrum than in 

 the Crocodiles. 



* Crocodilus prisons , Soemmerring. 



t De Natura Animaliuni, lib. x. sect, xxi, Jacob's Ed., 8vo, vol. i. p. 228. 



t Ossem. Fossiles, 4to, 1824, torn. v. pt, ii. p. 137. 



