Permo-Carboniferous Ammonoids of the Glass Mountains 143 



others, while the inner lateral point seems to be a little more prom- 

 inent than the outer one. The first auxiliary lobe is very little asym- 

 metrical and trifid, the middle point being much longer than the other 

 two, the outer one of which is a little shorter than the inner one. These 

 three lobes decrease in width and depth from the first one to the third. 

 The second auxiliary lobe is. very narrow, funnel-shaped, and sym- 

 metrically bifid; the connection between it and the following saddle on 

 the umbilical wall could not be made quite clear. 



The internal saddles are all high, slender, rounded, entire, and, with 

 the exception of the fourth, conspicuously constricted at their base. 

 They decrease steadily in height, but the fourth is a little wider than 

 the first three and not constricted. 



Dimensions : 



I 



Diameter 12.9 mm (1) 



Width 9.9 mm 0.77 



Height of last whorl 5.8 mm 0.45 



Diameter of umbilicus. . . 2.8 mm 0.22 



IV 



Diameter 11.3 mm (1) 



Width 9.6 mm 0.85 



Height of last whorl 4.7 mm 0.42 



Diameter of umbilicus. . . . 2.8 mm 0.25 



Relation to other species: 



M. vidriensis is easily distinguished from M. J. P. Smithi n. sp. 

 by its larger umbilicus, the more trapezoidal than semilunar cross-sec- 

 tion, the deeper constrictions, the narrower interstices between the 

 transversal striae of the ornamentation, by the different inner septa, 

 and especially by the narrower first auxiliary saddle and the less ir- 

 regular form of the trifid lobes. 



From M. sulcatus n. sp., it differs through the much larger umbili- 

 cus, the more trapezoidal cross-section, the straighter constrictions, 

 the flatter flanks and less rounded ventral portion, the different form 

 of the trifid lobes, which in M. sulcatus do not show the prominent 

 middle point, the narrow fourth lateral saddle, and generally the nar- 

 rower saddles and wider lobes. 



M. Hargisi n. sp. has an entirely different suture, and is also of :i 

 much more globose form. 



