NATURAL SCIENCES OF PHILADELPHIA. 113 



ence at any late period, with the nasale ; its ordinary positioa is traversed by 

 the frontal suture. The frontal bone is decurved, and closes the preorbital 

 aspect of the superpalatal vacuity, usually open. 



This marked genus, so abundantly represent'^d by individuals in the eastern 

 district of North America, is not admitted by either Dumeril or Hallowell, 

 probably because it does not differ in external characters from Plethodon. It 

 is an excellent illustration of the error of adhering to external characters 

 only, in the explanations of the relations and affinities of organized beings, 

 except for a limited range. Tlie examination of the slieleton of species of 

 this genus utterly changes the impressions produced by a consideration of 

 the external characters. It may be stated as characteristic of the Batrachia 

 in general, that their affinities cannot be determined without study of the 

 skeleton.* 



There are no dermal appendages developed in this genus at the breedini? 

 season. 



I. Males with posterior half mandible concave and edentulous. 

 Inferior lateral series of pores imperfect or wanting, superior none ; no 



tubercule in canthus oculi. Tail rounded. Fourteen costal plicte. A yellow- 

 ish dorsal band ; belly immaculate. Size small D. o c h r o p h as a. 



II. Males with mandibular alveolar margin continuous and completely 



toothed. 

 Inferior lateral series of pores well developed, superior irregular or want- 

 ing ; a tubercle in canthus oculi; tail compressed, and keeled; four- 

 teen costal plicae. Above dark spotted, below marbled. Size medium. 



D. f u s c a. 

 Two well developed lateral series of pores, a marked tubercle in the can- 

 thus of the eye ; tail flattened, finned above, attenuate ; twelve costal folds. 

 Black above and below. Size large D. nigra. 



Desmognathus ochroph^a Cope. 



Proceed. Acad. Nat. Sci. Phila. 1859, 122. 



This small species bears a strong resemblance to the Spelerpes b i 1 i n e a- 

 tu s Green, and apart from generic characters, may be known from it by the 

 rounded tail, the paler colored abdomen, and the light bar from the eye to 

 angle of the mouth. Its proportions are stouter than in Plethodon e r y t h r o- 

 n t u 3, to which it also bears some resemblance. 



The costal folds are thirteen, but fourteen, if that which is immediately 

 above the groin be counted. The first falls immediately into the axilla. This 

 is the characteristic arrangement in D. f u s c a also, while in D. u i g r a the 

 fold above the groin usually extends to it, and is the twelfth, while that which 

 corresponds to the first of the species before named falls just in advance of 

 the axilla. Though this is typical of D. n i g r a, occasionally another plica 

 appears above the groin, and the twelfth is slightly in front of it. 



The pores in D. ochrophasa are very difficult to observe; in a fevf 

 specimens I have seen a few of those of the lower series, the upper I believe 

 to be wanting. The gular fold is distinct, and another vertical fold com- 

 mences behind its extremity, and turning longitudinally extends more or less 

 distinctly to the orbit. As in other species the derm adheres closely to the 

 frontal bones and is more or less rugulose. The head is oval with rounded 

 depressed muzzle; its greatest width enters the length to the groin 5f times. 

 The commissure of the mouth is slightly flexuose. 



The appressed limbs fail to meet by four intercostal spaces. The inner digits 

 of both feet are short, but free ; longer than in Plethodon species of similar 

 size; the other digits are also longer and more distinct; proportions, I — 4 — 2 



* The skeletons on which the present observations are based are in large part the prep" 

 arations of Prof. Baird. 



1869.J 8 



