THE AMERICAN COAL MEASURES BRANCHIOSAURID^. 



53 



rise to the modem salamanders. The parts preserved in the specimen are: the 

 complete outline of the head with most of the cranial elements clearly distinguish- 

 able, as well as the black pigment of the choroid; the entire vertebral column, in- 

 cluding pits in the tail region, where the vertebrae were without doubt entirely car- 

 tilaginous; parts of the pectoral girdle; the ilium; the left humerus; the ventral 

 scutellation ; the ribs of one side of the body and indications of ribs on the other; 

 portions of both hind limbs; and a complete impression of the fleshy tail. On this 

 impression of the tail are preserved small, homy scales, transverse color-markings, 

 and the distinct impressions of the lateral -line system. 



The bones of Micrerpeton caiidatum, as in so many of the fossils from this local- 

 ity, have been replaced by a white, friable mineral which is probably kaolin. The 

 animal is preserved on its back and it is thus illustrated from the ventral side. The 

 entire length of the animal is only 49 mm., of which the tail occupies nearly half. 



The head has miuch the same shape as in the species of Branchiosaurus described 

 and figiu-ed by Fritsch (251), Credner (181), and Thevenin (568). The eyes occupy 

 relatively the same position as in that genus. The orbits are very large and broadly 



Fig. 13. — Restoration of Micrerpeton caudatum, a. branchiosaur 

 from the Coal Measures of Illinois. X 2. 



oval. Within the borders of the rim the stone is blackened as though by the black 

 pigment of the iris, such as Cope has described in Amphibamus. Under a rather 

 high power of magnification the cranial bones are seen to be represented by mere 

 flakes of white mineral matter. The sutures separating the cranial elements are 

 distinctly preserved on the main half of the nodule. 



The openings of the skull are five — the two orbits, the two minute nostrils, and 

 the pineal foramen. A median suture separates the skull into halves and the pineal 

 foramen lies slightly anterior to the posterior third of its length. The boundaries 

 of the premaxillae are not distinct, but they are very small elements and form the 

 inner border of the nostrils, which are clearly indicated by bosses of stone. The 

 nasal element is nearly square and lies anterior to the frontal, which it borders 

 broadly. The parietal is about the same size as the frontal and it apparently forms 

 a portion of the inner border of the orbit, although this is not assured. The parietal 

 is elongate and unites posteriorly with the postparietal. The postparietal, with the 

 tabulare and the squamosal, form the posterior boundary of the skull, and they are 

 hence not unlike the same elements in other Stegocephala. The prefrontal forms 

 the anterior border of the orbit. The lacrimal has not been detected. The maxilla 



