52 THE COAL MEASURES AMPHIBIA OF NORTH AMERICA. 



the fore limb is usually larger than the hind limb, the reverse of which is the case in 

 Pelion. The genus Sparodns, as it occurs in North America, is uncertain. It is 

 indicated by remains which are almost impossible of determination. 



The genus Micrerpeton may be distinguished from other known Branchiosauria by 

 the large size and anterior position of the orbits, absence of a posterior table to the 

 skull, the short, heavy limb bones, the slender ilium, and the expanded, elongate, and 

 laterally compressed tail. The genus may be defined as follows: Small forms, the 

 known representative attaining a length of less than 2 inches ; head broad and short ; 

 sclerotic plates present ; interorbital space less than the least diameter of the orbit ; 

 occiput concave; pineal foramen in the line which cuts the posterior edge of the 

 orbits; teeth small, pleurodont denticles; presacral vertebrae 20 or 21, of which 

 probably 5 are cervical; i sacral; ribs short, straight, and heavy, central; scapula 

 ovoid ; limbs stumpy and heavy, fore limb exceeding the hind in size ; endochondral 

 ossifications distinctly absent; tail long, expanded, and flattened, probably provided 

 with a thin expanded membrane; body covered with minute, ovoid or rounded 

 scales which are ornamented with concentric lines; color markings vertical to the 

 long axis of the body and abundantly present on the tail ; lateral-line organs repre- 

 sented by the dorsal and median lateral lines on the tail, the sensory pits probably 

 occurring in specialized darkened scales. Coal Measures of Mazon Creek shales 

 near Morris, Grundy County, Illinois. 



Micrerpeton caudatum Moodie. 

 MooDiE, Jottr. Geol., 17, p. 39, figs. 1-6, 1909. 



Type: Specimen No. 12,313, Walker Museum, University of Chicago. 



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



The species is represented by very complete remains (plate 2), which are pre- 

 served on opposite halves of a nodtile. The specimen was collected many years ago 

 by Mr. W. F. E. Gurley at Mazon Creek, but it has never before been studied, 

 although Dr. Newberry examined it and said in a note that Professor Cope should 

 see it. Unfortunately Cope did not see it and it lay unknown for more than a quar- 

 ter of a century. I am indebted to Dr. Stuart Weller for calling my attention to the 

 specimen, as well as for the privilege of describing it. 



The specimen is exceptionally perfect (plate 25, fig. 4). Nearly all the skeletal 

 elements are present, and the general contour of the body, the character of the dermal 

 covering, the color-markings, the lateral-line system, and many other features of 

 interest have been detected. Such completeness of preservation is very uncommon 

 even among the remains obtained from this locality. In this case the entire form 

 was preserved, but the collector, in cracking the nodule, lost the chips containing 

 the feet, so that only portions of the limbs remain. It is thus impossible to deter- 

 mine the phalangeal formula, but the feet were probably like those of Branchio- 

 saurus amblystomus Credner, as given by Credner, to which species the present form 

 is closely allied and indeed must be placed in the same family with Branchiosaurus, 

 Pelosaurus, and Melanerpeton. 



The remains here described represent a small, salamander-like form, and they 

 are among the earliest geological evidence of the group, which, without doubt, gave 



