132 THE COAL MEASURES AMPHIBIA OF NORTH AMERICA. 



tially preserved. The interclavicle is very large and from it the species has been 

 given its specific name (thoracatus armed with a breast plate) . It is an exaggerated 

 T, with the stem very short with its anterior margin curved, and ending in a rather 

 sharp, elongate point. The interclavicle recalls, in a measure, the same element of 

 the Branchiosauria, although it is much more expanded anteriorly and has a shorter 

 spine. In these respects it resembles more nearly a reptilian interclavicle (fig. 14 B). 



The clavicle is of the simple triangular shape so characteristic of the Microsauria. 

 It is somewhat displaced backward and its inner margin is slightly obscured. The 

 humerus is elongate, apparently cylindrical, and with expanded ends, resembling 

 very closely the humerus of Amphibamus grandiceps, although its proportions are 

 much greater than in that species. Its length is almost equal to the length of the 

 skull, while in A. grandiceps the length of the humerus is only half that of the skull. 

 The radius (ulna?) resembles in its general proportions those of the humerus. It is a 

 more elongate, slender, lighter bone. The impression of the other bone of the fore- 

 arm is obscured. 



A portion of a single vertebral centrum from the posterior part of the dorsal 

 series is preserved. It is apparently amphiccelous ; its width is nearly half greater 

 than its length. 



MEASUREMENTS OF THE TYPE OF AMPHIBAMUS THORACATUS MOODIE. 

 (No. 4306, U. S. National Museum.) 



mm. mm. 



Length of entire specimen, as preserved 60 Greatest transverse diameter 3 



Length of skull impression 18 Length of humerus 10 



Greatqst width of same 15.5 Greatest diameter of same 4 



Long diameter of right orbit '. . 4 Least diameter of same 1.5 



Transverse diameter of same 3 Length of radius (ulna?) 1 1 



Transverse width of interclavicle 14 Length of vertebral centrum 2 



Long diameter of same 7(?) Width of same 3 



Long diameter of clavicle 



Genus CEPHALERPETON Moodie. 



MOODIE, Kans. Univ. Sci. Bull., vi, No. 2, p. 349, 1912. 



Type: Cephalerpeton ventriarmatnm Moodie. 



This genus is founded on remains of a nearly entire individual of a relatively 

 large microsaurian from the Mazon Creek shales. The genus is most immediately 

 related to the Amphibamidae, of which two species are already known, Amphibamus 

 grandiceps Cope and A. thoracatus Moodie. The present genus differs from these 

 species in many respects, notably in size. The skull in Cephalerpeton is nearly as 

 long as half the entire body of Amphibamus grandiceps Cope, inclusive of the tail. 

 Other structural differences are the anisodont teeth, the large size and the more 

 median position of the orbits, and the absence of the posterior tympanic notch 

 in Cephalerpeton. The form of the skull recalls that of Melanerpeton and Pelo- 

 saurus (190) of Europe, but those genera are branchiosaurian, while the present 

 form, from the structure of the vertebras and the long, curved ribs, is an un- 

 doubted microsaurian. Nothing like it occurs in any of the amphibian faunas 

 thus far made known. It is most nearly approached by a member of the genus 

 Erpetosaurus, but from this genus the present form is readily distinguished by the 

 smooth skull bones, the absence of a posterior table to the skull, and the presence 

 of a highly developed ventral armature. The interorbital width is less than the 

 transverse diameter of the orbit. 



