70 THE COAL MEASURES AMPHIBIA OF NORTH AMERICA. 



Erierpeton branchialis Moodie. 

 MooDiE, Kans. Univ. Sci. Bull., vi, No. 2, pp. 329-330, pi. i, fig. 3; pi. 2, fig. 1, 1912. 



Typ>e: Specimen No. 8oi (222) 5, Yale University, Museum. 



Horizon and locality: Mazon Creek shales, near Morris, Illinois. 



The amphibian remains designated by the above name consist of a distinct man- 

 dible and some rather indefinite body impressions (plate 3, fig. 4). Three elongate 

 impressions occur between the rami of the mandibles (fig. 15, A), which, I suppose, 

 must represent hyoid bones belonging to the hyobranchial arches. The lateral ele- 

 ments are paired and the median impression is straight and lies between the paired 

 impressions of the hyoids. The paired portions probably represent the hypohyals 

 or hypohyals plus the ceratohyals, and the unpaired portion of the first basibranchial, 

 according to the nomenclature of Wiedersheim (Comparative Anatomy of Verte- 

 brates, 1897, p. 86). If the impressions have been correctly interpreted the present 

 specimen is of very great interest, since it is the first evidence we have of the hyo- 

 branchial arches in the Amphibia of Mazon Creek, and the second in the Carbon- 

 iferous of North America. Dawson doubtfully identified (216) some elements of 

 the Joggins Amphibia as hyoids, but was uncertain as to their position. Cope 

 described fully the well-developed hyobranchial apparatus of Cocytinus gyrinoides 

 (123) from the Coal Measures of Ohio. Among other Paleozoic Amphibia Williston 

 (614) has described branchial arches in the peculiar form Lysorophus iricarinalus 

 Cope, from the Permian of Texas. 



The form of the impression of the mandible in the present specimen is unlike 

 anything known to the writer among other Carboniferous or later Amphibia. The 

 rami are long, slender, deep, slightly curved, and pointed anteriorly. The anterior 

 symphysis was not a complete sutural union, but was occupied partly by cartilage 

 or other connective tissue. 



There are no definite traces of the appendicular skeleton. The traces of the body 

 (fig. 15, A) indicate an elongated, rather slender animal, but further than this noth- 

 ing can be said in regard to its structure. 



The occurrence of a typically caudate form in the Carboniferous is unusual and 

 complicates still further our understanding of the origin and relationships of the 

 early Amphibia. 



Measurements of the Type. 



mm. mm. 



Length of entire impression 50 Width of basibranchial 0.75 



Length of mandible along median line 10 Length of hypohyal 2.4 



Width of mandibular ramus 9 Width of hypohyal 1.5 



Length of basibranchial 2.5 



Genus HYPHASMA Cope, 1875. 



Cope, Proc. Acad. Sci. Phil., p. 16, 1875. 

 Cope, Geol. Surv. Ohio, 11, pt. 11, p. 387, 1875. 



Type: Hyphasma Icevis Cope. 



"Vertebrae osseous, the posterior dorsals, and probably the caudals, furnished with fan- 

 like neural spines; limbs unknown-(?) wanting. Thoracic shields present. Ventral arma- 

 ture, consisting of rhomboidal scuta, forming packed rows arranged in chevrons, directed 

 backwards, on top of which are the usual rod-like scales arranged in packed chevrons, with 

 the angle directed forward. 



