198 VERTEBRATE REMAINS, PORT KENNEDY BONE DEPOSIT. 



so convex as in Z. constrictor and Z. testaceus. As in those species, the basis of the 

 outer lamina continues for a short distance along the ramus as a low ridge, and on 

 the outer side of this, a short distance in front of the fossa, the mandibular foramen 

 issues. The cotylus for the os quadratum is large, and wider than in either of the 

 species named. The prootic displays the large maxillary and smaller ophthalmic 

 divisions of the foramen ovale, with a smaller foramen below the latter as in 

 Z. constrictor ; but the bridge separating the former two is narrower than in the 

 specimens of the two species with which I have compared it. 



In size this species is similar to the common black snake. The ramus of the 

 mandible measures .035 m. in length; and is .0045 in depth at the inner side of the 

 pterygoid fossa. The maxillary measures .0087 in length from the front of the 

 anterior to the posterior border of the posterior, inner, transverse process. The 

 length of a vertebral centrum is .006. The various details of structure already 

 mentioned indicate the specific distinctness of this snake from the two species of 

 the genus to which it is most nearly allied, and with which I have compared it. 

 Its pertinence to the genus Zamenis is demonstrated by the cranial bones fortu- 

 nately preserved. 1 



MAMMALIA. 



GLIRES. 

 ERITHIZON Cuv. 



But few remains of porcupines have been found in the Port Kennedy deposit, 

 and it is not possible to determine the exact specific relations of the animal they 

 represent. 

 Erithizon? dorsatum Linn. 



The Wheatley collection contains a superior molar, and the Academy collection 

 a mandibular ramus with two molars in place and molars of five other individuals 

 of this species. Three molars last found differ from the Wheatley tooth, and three 

 of the four differ from the corresponding teeth of the existing E. dorsatum., but in 

 different ways. An examination of ten crania of E. dorsatum gives the following- 

 results : — 



In the Wheatley tooth, the posterior lake is transversely divided (in the long- 

 axis of the jaw) so as to leave an internal smaller and an external larger lake or 

 fossa. In E. dorsatum the posterior lake is longitudinally divided (transverse to 

 the axis of the jaw) into an anterior larger and a posterior narrower fossa. This 

 division results frem the development of a posterior transverse cingulum ; or at least 

 the occasional imperfection of the posterior wall gives that impression. This is also 

 the character of one of the Port Kennedy molars. In a single skull of E. epixan- 

 thum at my disposal, the division appears to have resulted from the development of 

 a transverse fold within the posterior fossa. In two of the Academy molars the 

 posterior wall is duplicated near the middle, below the unworn apex, so that in an 



1 These specimens have not been found in the collection as transferred to the Academy. 



