160 



same proportional extent behind the last alveolus of the upper jaw. The eye- 

 lids and opercular flaps of the ear, and the tegumentary valvular nostrils, with 

 other portions of the integument, are left upon the exterior of the skull. There 

 are no palpebral ossicles. The number of alveoli is, in the premaxillary, 

 5 5 ; in the maxillary, 14 14 ; in the dentary, 15 15. Mm. Srit. 



727. The skull, wanting the lower jaw, of the Crocodilus biporcatus. The back part 



of the skull is broken away, and a portion of the descending process of the 

 basioccipital has been removed by the saw, to show the common descending 

 canal of the median system of eustachian tubes, and one of the lateral eusta- 

 chian canals, with the sinus of communication between the lateral and the 

 basioccipital branch of the median canal *. The number of alveoli is, in 

 the premaxillary, 4 4 ; in the maxillary, 14 14. 



Presented by Prof. Owen, F.R.S. 



728. A mutilated cranium of the Crocodilus biporcatus, in vertical and longitudinal 



section. The small petrosal may be noticed at the bottom of the T-shaped 

 suture, uniting the alisphenoid with the ex- and super-occipitals. The common 

 canal of the median system of eustachian tubes is laid open to its bifurcation 

 into the basioccipital and basisphenoidal branches, and the subdivision of each 

 of these into a pair of canals diverging laterally to the tympanic cavities is 

 shown. The tympanic cavity is exposed in the left half of the section by the 

 removal of the basi- and ex-occipitals. The number of alveoli is, in the pre- 

 maxillary, 44 ; in the maxillary, 14 14. Presented by Prof. Owen, F.R.S. 



729. The six pieces of which the composite ramus of the lower jaw of a Crocodile is 



composed. Each is indicated by its characteristic number, and has also its 

 name marked on it. Presented by Prof. Owen, F.R.S. 



730. The right ramus of the mandible of the Crocodilus biporcatus, in four transverse 



sections, showing the mode in which the pieces are articulated together and 

 their texture. 



* This specimen is figured in PI. 41. fig. 7 of the donor's 'Memoir on the Communications between 

 the Cavity of the Tympanum and the Palate in the Crocodilia,' Phil. Trans. 1850, p. 521. 



