156 University .of Texas Bulletin 



broader toward the top. In Hyattoceras the external saddle ends In 

 two phylloid points and the lateral and auxiliary saddles in one. In 

 Waagenoceras all the saddles end in one phylloid point of remarkable 

 size. In Hyattoceras all the saddles are parallel to each other, while 

 in Waagenoceras the external saddle is strongly bent over toward 

 the siphonal region. The median saddle of the siphonal lobe is higher 

 in Waagenoceras than in Hyattoceras and the number of lateral and 

 auxiliary lobes is larger in the first genus than in the latter. 



These differences permit of distinguishing both genera at once. 

 Especially characteristic is the line which is followed by the suture, 

 straight in one genus and curved in the other; the form and position 

 of the external saddle ; and the form of the saddles in general. 



When we now compare the Texas forms with those of Sicily we 

 must take into consideration that JV. Cununinsi is known only in 

 small individuals and that the suture is apparently not qviite well pre- 

 served, while W. HUH is a large specimen the septa of which are of 

 course much farther divided. In both species the median saddle of 

 the siphonal lobe is very high, all the saddles end in one phylloid point, 

 but are much broader at the base than at the upper end; while the 

 lobes, including the branches of the siphonal one, decidedly end in 

 one long point.-^ All the saddles are parallel to each other and the ex- 

 ternal ones do not lean over toward the sipho; the suture follows a 

 straight line. 



Thus the Texan forms distinguish themselves from Waagenoceras 

 by their smaller number of lobes, the form of the saddles broad below 

 and narrow above and that of the lobes, ending in a prominent point 

 and broad above ; while in Waagenoceras the saddles and lobes, gener- 

 ally speaking, are equally broad in the whole length. Furthermore, the 

 Texan species do not show, like Waagenoceras, an external saddle 

 leaning over toward the sipho; on the contrary, it stands erect and 

 is parallel to tlie lateral saddles. The lobes of the Texan species end 

 in one prominent point while those in Waagenoceras are rather digi- 

 tate. The suture of the Texan species follows a straight line while that 

 of Waagenoceras follows a strongly convex line. 



'This is not as evident in the figure o£ W. HiUi given by J. P. Smith as it can be 

 seen to be in the original, which is in my hands. 



