50 BULLirriN 34, UNITED STATES NATIONAL MUSEUM. 



lu tbis connection it is desirable to ascertain how far characters tlis- 

 tingnishing undoubted species fall into the line of successional changes 

 common to all the species, as answer to this question would solve an 

 importaut part of the iuquiry as to the origin of species. We can not go 

 into it exhaustively at this time, but direct attention to these char- 

 acters in the synoptic table. The following are developmental char- 

 acters which distinguish known species: (1) The direction of the pala- 

 tine series of teeth; (2) the length of the body and tail, as compared 

 with the width of the head, is greater in large and old individuals of 

 A. tigrinum ; (3) the widening of the muzzle and greater separation of 

 the external uares ; (4) the spotted as distinguished from the uniform 

 coloration. 



Characters to which no such relation can be assigned: (1) Thenumber 

 of costal folds, whose interspaces correspond with the vertebrse ; (2) the 

 number of phalanges. 



Baird, in the first synopsis of this genus published, enumerates eight 

 s])ecies ; Gray in 1850 catalogues ten, after we exclude some species of 

 other genera erroneously included. Dumeril, likewise including species 

 of other genera, gives five true Amblystomte. Hallowell, 1858, increased 

 the number to sixteen. In my monograph of tbis genus, published in 

 1867, the species described numbered eighteen, six new^ ones being 

 added. Dr. Boulenger, in the Catalogue of the British Museum, second 

 edition, published in 1882, gave the number as seventeen, including a 

 Siamese species. In the present work thirteen species are admitted, one 

 of which is the Siamese species A. persiniilis, after the subtraction of 

 nine species placed in the genera Ghondrotus and Lingucdapsiis. For 

 the study of this genus the collection of the Smithsonian Institution is 

 unequaled. Probably the second best collection existing, that of the 

 Academy of Natural Sciences of Philadelphia, has also furnished its 

 numerous types, and several species mostly described by the late Dr. 

 Edward Hallowell. 



Synopsis of species. 



I. Scries of teeth extending along the exterual iissu'jo of the iuternal uares. Plicae 

 of tongue radiating from its posterior portion. Parotoid glands not 

 forming an ovoid distinct mass. Four phalanges in fourth toe." 



A. Costal grooves, ten. 



a. Vomerine series, three. 



Head broad; width 3.5 to groiu ; muzzle contracted ; external uares much 

 closer than internal ; palatine scries convex backwards; tail short, 

 compressed ; blackish-hrown, gray specked A. lalpoideiim. 



B. Costal grooves, eleven. 



a Vomerine series three. 



j.i No, or one indistinct iilantar tubercle. 



Middle series transverse or concave to behind posterior margins of uares; 

 width of head in specimens of 3 inches, greater tbau oue-foiu'th lengtli 

 to groin; in adults, 4.7 times ; black above, with gray cross-l>ands. 



A. opactnn. 



* Vide au oxceptiou iiniler A. (iijiinum. 



