94 PROCEEDINGS OF THE ACADEMY OF 



the present family. On the other hand, the non-prolongation posteriorly of 

 the vomers, and the amphicoslian vertebrae, belong to this family and the Am- 

 blystomidaj only. The position of the latter family is therefore between the 

 Plethodontidae and the Salamandridse. The Amblystomidaj and Plethodon- 

 tidce may be thus compared with reference to the developmental character of 

 the features which distinguish them. 



Amblystomid.e. Plethodontid^. 



Superior. Inferior. 



Carpus and tarsus osseous. Carpus and tarsus cartilaginous. 



Premasillary fontanelle closed. Prema.xillary fontanelle open. 



Inferior. Superior. 



0. pterygoideum persistent. 0. pterygoideum obliterated. 



The inferiority of some Plethodontidae is seen in the non-distinction of the 

 digits (Geotriton), the thinness of the ossification of the parietal membrane 

 boues (Batrachoseps), and in Opheobatrachus 1 i n e o 1 u s m, from Vera Cruz, 

 the persistence of the membranous cranium by the limitation of the parietal 

 bones to two small lateral scales, and the wide divarication of the posterior 

 extremities of the frontals. 



Most characters of this family are those of low development, and approxi- 

 mations to the larval condition, except the loss of the pterygoid : two of the 

 species exhibit a subocular cirrhus, which occurs in some of the Gymnophidia 

 (Coecilia) and Dactylethra among Anura. It is probably the persistence of 

 that long subocular tentacle characteristic of the early larval stage of Sala- 

 mandridie and Pleurodelidaj (e. g., Salamandra Notophthalmus), and of a 

 later larval stage of Dactylethra (vid. Wyman and Gray), where they resemble 

 the appendages of the Silurida. They have been called crochets by Rusconi, 

 and homologized with the cylindric cephalic processes of the larval Rana, 

 with what correctness remains to be proven by observations on other types, 



Eschscholtz correctly represents Batrachoseps attenuatus as without 

 prefrontals. An elongate process of the frontal occupits only part of its place, 

 forming no suture with the maxillary ; this is quite different from Desraogna- 

 thus, where the orbit is completed by the union of frontal and maxillary. la 

 Batrachoseps quadridigitatus the prefrontal occupies this depression 

 as an elongate vertical scale. 



In Spelerpes rubra the quadratum presents a small internal anterior ala, 

 which has a superficial resemblance to a pterygoid. In this species there is 

 apparently an azygus bone behind the premaxillaries ; this is, however, only 

 the exposed extremity of their united spines, which are nearly or quite isola- 

 ted by the approximation of the anterior parts of the nasale. It does not 

 occur in the Gyrinophilus salmoneus. 



The genera embraced in this family appear to be as follows : 

 Section I. The tongue attached from the central or posterior pedicel to the 

 anterior margin in narrower or wider band. (Plethodontae). 

 A. Two premaxillary bones. 

 Digits 4 — 5 ; maxillary bone regular, with numerous small teeth ; parietals 



fully ossified Plethodom. 



Digits 4 — 4 ; maxillary as above, parietals fully ossified. Hemidactylium. 

 AA. One premaxillary. 

 a.. Digits 4 — 4. 

 Maxillary regular, with small teeth ; parietals not ossified.. Batrachoseps. 



eta.. Digits 4 — 5. 

 Maxillary normal, teeth small, very numerous ; no premaxillary fontanelle. 



Stereochila. 



Maxillary edentulous posteriorly, decurved, forming a cutting edge ; teeth 



few, large, knife-shaped; a premaxillary foutanelle Anaides. 



[May, 



