THE MICROSAURIAN FAMILY STEGOPID^. 



113 



quite distinct, in spite of Jacket's protestations to the contrary. The genus Stegops 

 stands alone among the Carboniferous Amphibia of North America, so far as I am 

 aware, in the possession of a well-defined lacrimal of the labyrinthodont type. 



Stegops divaricata Cope. 



COPE, Proc. Am. Phil. Soc., xxn, p. 406, 1885 (Keraterpeton diiiaricattim) . 

 MOODIE, Jour. Geol., xvn, No. I, p. 79, fig. 22, 1909 (Stegops). 



The 



Type: Specimen No. 2559 G, American Museum of Natural History, 

 obverse of this is No. 12,311, Walker Museum, University of Chicago. 



Horizon and locality: Linton, Ohio, Coal Measures. 



The skull on which this species is based consists of the impressions on two slabs 

 of coal, one belonging to the Newberry Collection of the American Museum of 

 Natural History, No. 2559 G, and the other to the Gurley Collection of the Uni- 

 versity of Chicago, No. 12,311. The slab be- 

 longing to the University of Chicago contains the 

 better-preserved remains, so that the descrip- 

 tion is based largely on that portion (plate 25, 

 fig- 3)- Nearly all of the elements of the skull 

 are determined with considerable certainty and 

 many important characters in the morphology 

 of the Microsauria are thus brought out. 



The skull is oval, elongate, truncate behind, 

 and the quadrate angles project into sharp 

 horns. The orbits are elongate ovals and their 

 center lies in the median line which divides the 

 skull transversely. The nostrils are elongate 

 and have an oblique position. The pineal fora- 

 men lies in the posterior third of the skull. FlG 2 3 ._ S kull elements aTstogop, divaricata 



Teeth are preserved on both maxillae and pre- 

 maxillae. They are simply sharp pleurodont 

 denticles, and seem to have been fairly abun- 

 dant. The bones have been completely carbon- 

 ized and nothing of the original texture is preserved, although the details of the 

 structure are beautifully preserved. (Plate 25, fig. 3.) 



The skull is somewhat triangular in its general form. The premaxilla lies on 

 the anterior border of the cranium, and forms the median border of the nostril. 

 The suture which separates the maxilla and the premaxilla is not evident, and it 

 may not be correctly defined in the figure (fig. 23). The nasal is a very large 

 element and is elongate. It unites with the premaxilla, the lacrimal, the pre- 

 frontal, and the parietal. It is acuminate behind and the point is inclosed by the 

 pref rental and the parietal. The frontal is quite narrow and elongate, and does 

 not border the orbit; its posterior boundary is not accurately represented. The 

 radiations on the surface indicate the extent of the element. The parietals are 

 remarkable in being smaller than the frontal and nasal. The pineal foramen is 



Cope., fr, frontal; it, intertemporal ; j, jugal; 

 la, lacrimal; mx, maxilla; n, nasal; par, 

 parietal; pf, prefrontal; po, postorbital; pof, 

 postfrontal; pmx, premaxilla; sq, squamosal; 

 spt, supratemporal ; ijj, quadra tojugal; lab, 

 tabulare; pp, postparietal. X 1.3. 



