Permo-C arboniferous Ammonoids of the Glass Mountains 75 



With regard to. the suture, our species resembles M. bifrons Gemmel- 

 laro/ There we find the same kind of trilobate saddles, the very asym- 

 metrical siphonal branch of the external saddle, and the inclined 

 umbilical branch of this saddle, although the number of rudimen- 

 tary adventive lobes and of auxiliary lobes is much smaller, — a fact 

 which might be explained by the size, if the suture (Gemm., pi. 9, fig. 

 19) has not been taken from the specimen figured in Gemm., pi. 9, fig. 

 18. Another difference may be found in the lesser length of the um- 

 bilical branch of the external saddle in M. bifrons and the generally 

 broader lobes. The Sicilian species does not show the rows of tubercles 

 on the ventral keels, it is broader in the ventral part, and the ratio of 

 dimensions is somewhat different from that of M. Whitneyi. 



The suture of our species has a certain similarity also to that of M. 

 primas Waagenl There we find the same trilobate saddles, and the 

 inclined umbilical branch of the external saddle, but the adventive lobe 

 is much deeper and of different shape and the siphonal branch of the 

 external saddle is much less asymmetrical. 



A certain resemblance exists also between M. Whitneyi and M. 

 Burckhardti n. sp. In this latter one, we find the same kind of trilo- 

 bate lateral saddles, but they are longer and more slender. The umbili- 

 cal branch of the external saddle, Esz, is very little inclined and nearly 

 parallel to the lateral saddles and not very much smaller. In a speci- 

 men a little larger than that of M. Whitneyi, the siphonal branch of 

 the external saddle shows only seven rudimentary adventive lobes 

 instead of nine. Small specimens of M. Burckhardti show sharp ven- 

 tral keels and not a trace of tubercles. 



The other species found in Texas, M. Copei White'^, resembles our 

 species much less. It is broader at the venter, the saddles are not 

 trilobate but tongue-shaped, the adventive lobe A has an entirely dif- 

 ferent form, and the lobes are more asymmetrical. 



The circumstance that M. Copei is so entirely different from M. 

 Whitneyi is of some interest, because apparently they come from beds 

 of nearly the same age ; but we have to take into account the fact that 

 the fossils in both localities are very insufficiently known and that the 



'Gemmellaro, Calc. c. Fusulina, p. 51, pi. 9, fig. 16-19. 



''Waagen, Saltrange fossils, Productus limestone fossils, I, p. 39, pi. 2, fig. 7. 

 Noetling, Medlicottia und Episageceras, p. 355, pi. 17, fig. 1-a, 1-b, pi. 19, ng. 1. 

 "White The Texan Permian, p. 21, pi. 1, fig. 1-3. 



