164 REPORT OF NATIONAL MUSEUM, 1898. 



calcis. Both these elements have a distal convex condylar surface for 

 the elements distal to them. The tarsalia are partially aborted. 



No urinary bladder. A rudimental diaphragm. The viscera are 

 more particularly described under the genus Alligator. 



ALLIGATOR Cuvier. 



Alligator Cuvier, part, Ann. Mus., X, 1807, p. 30.— Dumkril and Bibron, Erp. 



Gc'n., Ill, 1836, p. 63.— Strauch, Syn. Crocod., 1866, p. 9. 

 Champsa Wagler, part, Syst. Ampli., 1830, p. 140. 

 Alligator GKA.Y, Cat. Tort., 1844, p. 66.— Huxley, Jouru. Linn. Soc, IV, 1860, p. 



3.— Gray, Cat. Sh. Rept., II, 1872, p. 28. 



Fourth mandibular tooth fitting into a pit in the upper jaw. Snout 

 rather short; nasal bones forming a septum dividing the nasal aper- 

 ture; supratemporal fossae open, splenial bones not entering the man- 

 dibular symi)hysis. A dorsal shield formed of juxtaposed, keeled, 

 bony scutes; gular and ventral scutes without or with thin ossifications. 



Osteology. — My knowledge of the osteology of this genus is derived 

 exclusively from the A. mississippiensis. 



Premaxillaries with the spine very short, and uniting by suture with 

 the i)roduced apices of the nasal bones. Lateral plate in considerable 

 sutural union with the nasals posterior to the nares. Frontal produced 

 in a narrow process between i)refrontals. A small supraorbital bone 

 anteriorly placed. Parietal-like frontal, undivided, not sending out 

 supramastoid processes, and extending to the posterior border of the 

 superior table of the skull. Supratemjjoro-mastoid sending out a latero- 

 posterior process almost to the extremity of the exoccipital, and bounded 

 below posteriorly by the quadrate, medially by the meatus auditoriusj 

 and anteriorly from before backward, by the quadrate, the superior 

 process of the zygomatic, and by the postorbital jDart of the j^ostfronto- 

 orbital. Anteriorly it is bounded by the postfrontal part of the post- 

 fronto-orbital. The articular surface of the quadrate is directed as 

 much backward as downward. The zygomatic reaches its distal 

 extremity in front, while the jugal is continued three-fourths way from 

 its first i)oint of contact with the zygomatic to its extremity. The 

 parieto-quadrate arch is not entirely fused with the elements lying 

 below it, as it is not united with the snpraoccipital by suture, except 

 on the middle line. The lateral part of the superior border of the supra- 

 occipital is a smooth tuberosity, and a foramen passes entirely below 

 the supratemporo-mastoid bone to the supratemporal foramen. Another 

 canal passes between the exoccipital and quadrate from behind for- 

 ward and inward to the temporal fossa. The snpraoccipital does not 

 reach the foramen magnum below, but the latter is inclosed above by 

 the exoccipitals. The latter do not enter into the composition of the 

 occipital condyle, which consists eritirely of the basioccipital. 



The quadrate is remarkably extended forward. Below, it sends 

 down a broad process to join the pterygoid, medially it joins the 



