Dr. J. E. Gray on the Species of Alligators. 327 



sunt, aliquando omnino absunt ; corpore subtus nigro ; antennis 

 fusco-uigris ; pedibus fusco-nigris, tarsorum articulis anteriorum 

 latis. 

 Magnitudine variat ; long. corp. lin. lf-14> lat. 4. 



A variable species, both in pattern and size ; nevertheless the 

 four examples before me (none absolutely identical with the 

 three others) evidently represent a single species, which is abun- 

 dantly distinct from all others with which I am acquainted : its 

 elongated form, coupled with the greater breadth of the post- 

 medial elytra (especially as contrasted with the thorax), and the 

 distinct angle formed by the line of the margins of the elytra 

 and thorax separate it at once from all species found in Great 

 Britain. In our list the name will stand next to H.palustris, Linn. 



Four examples of H. tinctus were detected among a mass of 

 Turner's captures, by my friend Dr. Power : they were captured 

 certainly in the district of the New Forest. 



XXXV. — A Synopsis of the Species of Alligators. 

 By Dr. J. E. Gray, F.R.S. &c. 



Having had occasion to re-examine the large collection of Alli- 

 gators in the British Museum for the purpose of naming the 

 more recently received specimens, I am induced to lay before 

 the readers of the ' Annals ' an abstract of the result of this 

 examination. 



I may observe that Spix, in his work on Brazilian Lizards, 

 gives very good figures of these animals, with the colours well 

 marked; and Natterer, in his 'Beitrage* on South-American 

 Alligators, gives very accurate and detailed figures of the head 

 and the neck-shield of the different species ; and he has figured 

 some varieties or species very nearly allied to those here noticed, 

 which I have not seen. 



The Alligators (Alligatoridcc) may be divided tnus : — 



I. The ventral scutella like the dorsal ones, bony, and articulated together, 

 forming a shield. The eyelids with an internal bony plate. The cervical 

 scutella in pairs, forming an elongated shield. Nasal bone short. Tro- 

 pical America. 



1. Jacare. The orbits united by a bony cross ridge. Eyelids 



partly fleshy, striated or rugose. 



2. Caiman. The orbits not united by a cross ridge. Eyelids 



entirely bony, smooth. 



II. The ventral scutella thin, the dorsal scutella bony, not articulated 

 together. The eyelids fleshy, smooth. The cervical scutella in pairs, sepa- 

 rate. Nasal bone elongate, separating the nostrils. North America. 



3. Alligator. The face broad, depressed. 



