THE MICROSAURIAN FAMILY TUDITANID^. IO7 



ing grooves and ridges, as in so many of the Microsauria. The interclavicle is 

 spatulate and bears a general resemblance to the same element of Metoposaurus 

 fni<isi Lucas from the Triassic (383) of Arizona. The clavicles are triangular, 

 with rounded angles and the hypothenuse on the interior border. 



MEASUREMENTS OF PECTORAL GIRDLE OF SPECIMEN No. 4539, U. S. NATIONAL MUSEUM. 



mm. mm* 



Width across the entire girdle 17 Length of clavicle 1 1 



Length of interclavicle 15 Width of clavicle, maximum 6 



Width of interclavicle 10 



Erpetosaurus acutirostris Moodie. 

 MOODIE, Bull. Amer. Mus. Nat. Hist., xxvi, pp. 349-351, pi. Ixi, fig. i, 1909. 



Type: Specimen No. 8598 G, American Museum of Natural History. 



Horizon and locality: Linton, Ohio, Coal Measures. 



The present species adds another form to the diversity of structure presented by 

 the Carboniferous Microsauria. It is closely allied to Erpetosaurus (Tuditanus) obtu- 

 sus Cope, from the same beds (Linton, Ohio), but differs from it especially in the 

 position and shape of the orbits and the acute form of the skull. Other characters 

 which amount almost to generic significance are found in the posterior prolongation 

 of the frontal and in the triangular form of the skull. Only the skull of the animal 

 is preserved. The character which is common to all members of the genus Erpeto- 

 saurus, the cranial rugosity, is present in this species on the squamosal and supra- 

 temporal. This character alone would not, however, suffice to separate the form 

 generically, but the general morphology and arrangement of the cranial elements is 

 such that reference to any other genus save Erpetosaurus would not be possible. 



The skull of E. acutirostris takes the form of a rounded triangle. Its base is 

 some 50 mm. in extent, and this width gradually narrows to 31 mm. across the 

 orbits and still more towards the snout. The form of the skull is not widely 

 different from that of the type species, E. radiatus Cope, but the differences are 

 sufficiently apparent. 



Nearly all the elements of the cranium can be detected (fig. 22, D). The bony 

 portion of the cranium has nearly all been lost, leaving only the impression; and 

 the matrix in which the skull was embedded has been forced up into the sutures 

 between the cranial elements, thus forming ragged ridges where the bones of the 

 skull joined. 



The position of the nostrils can not be determined accurately. The orbits are 

 placed well forward, a character common to several species of the genus. The inter- 

 orbital space is equal to the long diameter of the eye. The orbits are sep- 

 arated by narrow prolongations of the postfrontals and by the anterior por- 

 tion of the frontals. The frontals are remarkable in their great back- 

 ward extension. In E. obtusus the frontals are nearly confined to the inter- 

 orbital space. The parietals, which, on the median suture, inclose the 

 parietal foramen, lie well posterior, and the parietals and the tabulare are 

 small. A portion of the sculpturing of these elements has been preserved and 



