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PROCEEDINGS OE THE ACADEMY OP 



a portion of the table of the cranium exhibiting the usual medial depression, 

 and embracing portions of the postorbital and parbt il bones ; one of the 

 former is four in. sixl. long ; both are pitted medially (about 3 pits in an inch) 

 and marked with short coarse sulci posteriorly. The parietal* are 2 in. 9 I. 

 wide behind, and four inches wide between the anterior parts of the postorbi- 

 tttls. On what is probably the posterior part of the interorbital region (a small 

 part of the posterior margin of the left orbit is preserved) commence two 

 smooth shallow sulci 1 in. 21. apart, which are probably the posterior extremi- 

 ties of the superficial channels of the face of the Labyrintuodonts. Between them 

 the surface is pitted, (4 or 5 to the inch.) The parietal bones are throughout 

 longitudinally sulcate, (four and one-half to the inch), with obtuse ridges be- 

 tween. The parietal fontanelle was not discoverable, nor could the form of 

 the orbits be certainly determined, though they were probably not large. 



The teeth are of various Bizes, sometimes two inches long, and more slender 

 in proportion to the length than those of the Mastodonsaurus j a ege r i and 

 salamandroides; they are cylindrical, gently curved and acuminate, 

 without external sulci; of the minuter sculpture noihing could be said, as Prof. 

 C. had only examined the casts of the surface. In a few weathered sections 

 the involuted folds of the enamel are well displayed. They areTiot convolute 

 as in typical Labyrinthodonts, but perfectly straight and convergent to a mi- 

 nute central vacuity. In a tooth four lines in diameter there appear to be five 

 principal radii which attain the centre, about twenty which nearly approach it, 

 and thirty two shorter, none of which measure less than a half radius. These 

 radii, though exceedingly delicate, may sometimes be seen in longitudinally frac- 

 tured specimens. The roots exhibit a short conic pulp cavity. 



Having observed traces of similar radii in a small fluted tooth having an 

 oval seciion, much resembling some of those of Belodon (Rhytidodon), but 

 perhaps Compsosaurus Leidy, it had occurred to the speaker whether these 

 radii had any connection with the mineral constitution of the teeth. These 

 were all of black dolomite, the weathered portions, between the radii, white. 

 Radii and straight veins of other material were pointed out in some specimens 

 in his collection by Wheatley, as iron and copper pyrites aud silica, but these 

 were either eccentric or irregular. Inquiry is therefore suggested respecting 

 the existence of the labyrinthic structure in any of the above genera before 

 described. The form and sculpture assigned to Centemodon Lea render com- 

 parison with the new species unnecessary. 



The latter may be named Mastodonsaurus durus. The cranial bones on 

 which it is founded occurred in bed No. 15, a hard black shale, of Wheatley 's 

 section in Silliman's Journal Sci. Arts, 1861, 45, about 89 feet from the 

 bottom of the series, while the tooth last described is from near 40 feet 

 lower down, in Nos. 21 or 22. The Belodon comes from about 35 feet below 

 the last. . 



Geologists have inclined to indentify these beds with the upper Trias or 

 lower Jurassic. The identification of the Belodon and Mastodonsaurus points 

 most strongly to the age being that of the Keuper or upper division of Trias. 



July olst. 

 Dr. Bridges in the Chair. 



Fourteen members present. 



The following gentlemen were elected Members of the Academy : 

 Prof. A. Stille, Dr. Geo. H. Horn, Mr. J. G. Moore, Dr. A. Neb- 

 inger, Mr. C. G. Ogden, and Mr. Samuel L. Shober; and Mr F. Cowan, 

 of Washington, was elected a Correspondent. 



On Report of the Committee the following was ordered to be published : 



[July, 



