BEDS OF THE I'ERMIAlSr EPOCH IX XOHTII AMEUICA. 



289 





the type in tlie number of its crests, while the second, which is a httle larger, has them 

 7{ instead of 6{-. 



ERYOPS PLATYPUS Cope. Ichlhyeanthut platypus Cope ; Proc. Amer. Phil. Soc, 1877, p. 574. 



A reexamination of the type specimen of this species from 

 the Coal Measures of Ohio, preserved in the museum of Cohimbia 

 College, Xew York, enables me to refer this species to the Rhach- 

 itonii. The neural spines are distinct, showing that it belongs, 

 probably, to the Eryopidne, As the skull is not preserved I can- 

 not determine the genus positively, but refer it for the present to 

 Eryops. I append a figure of the posterior foot, which displays 

 the characters of the tarsus of this group for the first time. The 

 number of tarsals is as in a Theromorph reptile, except that two 

 elements represent the cuboid bone, as in the reptile Stereosternum 

 tumidwn Cope ; giving five elements in the distal tarsal row. 

 There is but one centrale and no intermedium. Two fragments 

 of caudal vertebra) adhere to the specimen (marked cv in the accompanying cut). 

 The lettering of the cut is as follows: Fi, fibula; F, ni)ulare ; T, tibiale ; c, centrale; 

 i-v, tarsalia. 



Z.\TKACHYS SERRA.TUS Cope; Proceedingsof the Amer. Philos. Soc, 1878, p. 523 ; American Naturalist, 1884, p. 36. 



This species has been thus far certainly known from a portion of the maxillary 

 bone only. Analogy of general characters led me to associate with it a second species 

 under the name of Z. apicalis. This form was clearly rhachitomous, so that in the 

 American I^Taturalist, as above cited, I referred the genus Zatrachys to the family of 

 the Ei"yopid:Tc. 



A skull of the Z. serratus having come to hand, I am able to give some of its 

 characters. These indicate that the position assigned to it as above is correct, and 

 that it represents a genus dificrent from any of the others of the fiimily so far as our 

 present understanding of the characters goes. 



There are two approximated occipital condyles. There is no distinct basi-occipital 

 bone distinguishable, and it is possibly wanting. The palatopterygoid arch is convex 

 outwards, keeping near the maxillary bone, and separated from the parasphenoid by a 

 wide foramen. The intercalare forms a prominent angle on each side of the cranial 

 table. The occipital asjiect of the skull displays fontanelles between two ascending 

 portions of the exoccipitals, one of which bounds the foramen magnum, and the other 

 the intercalare. The latter has a superior ;iiul inferior posterior angle which are sepa- 



