NATURAL SCIENCES OF PHILADELPHIA. Ill 



Vertebral opisthoccElian. 



Carpus and tarsus osseous. 



Dcntigerous plates oa the paraspheniod. 



This family combines the peculiarities of the Desmognathidae, Plethodontidae 

 and Amblystomidae in a remarkable manner. The well developed opisthocce- 

 liaa vertebrae are characteristic of the first named and of the Salamandridas, 

 the fully ossified tarsus and carpus of the Amblystomidae. The dentition is 

 entirely that of the PlethodontidcC. This was the less to have been anticipated, 

 as the general characters of the only genus are those of the genus Spelerpes. 

 The history of the metamorphosis is as yet unknown. The only known genus 

 is Mexican. 



THORIUS Cope. 



Parietal and palatine bones rudimental, represented by cartilage and mem- 

 brane. Posterior nares therefore not separated from orbit; sphenoidal patches 

 of teeth entirely united ; tongue boletoid, free in front. Toes distinct, rudi- 

 mental, 4 — 5. 



The tarsal bones consist of astragalus, calcaneum, a scaphoid and three 

 minute cuneiform bones. The metatarsals and phalanges are fully ossified, 

 as are the corresponding elements of the fore limbs. 



This genus is higlily interesting, as indicating the lowest grade of ossific 

 deposit found among the tailed Batrachians, accompanied by characters of full 

 development in other respects. Thus, while the cranium is but imperfectly 

 ossified, and less developed than in a comparatively early larval stage of Ambly- 

 stoma, the tongue, vertebral column, and extremities have advanced far 

 beyond its larval condition, which is permanent in the latter genus, and the 

 branchial apparatus disappears while the individuals are but little more than 

 half their adult size. 



It is represented as yet by but one species, from Mexico, of terrestrial 

 habits. 



Thorius PENNATULua Cope. 



American Naturalist, 1869, 222. 



This is a small species, with smooth skin, very weak limbs, and stout tail. 

 The head is scarcely wider than the neck ; it is not flattened, the loreal region 

 is rather elevated and distinct, and the muzzle slightly prominent. The upper 

 lip is sometimes truncate, with infranarial angle prominent, sometimes regu- 

 larly rounded. The nostril is larger than any known salamander, its diameter 

 equalling half that of the pupil. 



The vomerine teeth are situated on a transverse, elevated crest, which is a 

 little behind between the inner nares, and though curved backwards, is but 

 little interrupted medially. Each half contains four teeth, perhaps five when 

 complete. The sphenoidal series is large, pyriform, the anterior extremity 

 narrowed and prolonged to opposite ihe middle of the orbits. 



There are thirteen costal folds ; three and one-half of their interspaces are 

 covered by the extended hind limb, from its origin. The toes are very 

 small ; only the three median behind and three outer before are developed be- 

 yond the metatarsus. The phalanges are, anteriorly — 2 — 2 — 1 ; posteriorly 

 — 2 — 2 — 2 — 0. Their extremities are distally free; that of the median poste- 

 rior projects more beyond those adjacent than in 0. lineolus. The costal 

 plicaB are not marked on the dorsal, and only on the ventral in the color vari- 

 ety mentioned. The tail is stout, and for a short distance at the base subquad- 

 rate in section, and nearly as thick as the body ; distally it is more compressed, 

 but is not keeled; length equal to that of head and body. The width of the 

 head enters 6-5 times, and the length in front of the axillae 3-33 times the 

 length to the groin. 



The color is brown, yellowish and clouded below, the dorsal region covered 

 with a gray band, which extends to the end of the tail. This band is particu- 

 larly light and slightly metallic on its margins, which are undulate or serrate, 



1869.] 



