142 University of Texas Bulletin 



than the saddles. The siphonal lobe is divided in two branches by a 

 median saddle. Each of the branches is asymmetrical and bifid, the 

 inner point on the siphonal side being much longer than the outer one. 

 The first and second lateral and the first auxiliary lobes are trifid, the 

 middle point being considerably longer than the two lateral ones ; these 

 latter are of nearly equal length; the inner one seems to be very 

 slightly longer. These three lobes are almost of equal width, while 

 the depth diminishes somewhat from the first to the third one. The 

 second auxiliary lobe is asymmetrical and bifid, the outer point being 

 much longer than the inner one. It .is much shallower and narrower 

 than the first three. A third auxiliary labe exists on the umbilical 

 wall ; it ends in one point, is funnel-shaped, and much smaller than any 

 of the others. 



The siphonal saddle is relatively high and slender; it is slightly 

 notched at the top by a shallow indentation and constricted near the 

 base. The external and the two' lateral saddles are very similar in 

 shape; their height decreasing very little from the first to the third 

 while their width is practically equal. The saddles are generally nar- 

 rower than the intervening lobes. The first auxiliary saddle is much 

 shorter and narrower than the external and the laterals. The second 

 auxiliary, which exists on the umbilical shoulder, is very broad and 

 low, and is not constricted at its base. A third auxiliary saddle lies 

 in its greater part on the umbilical wall ; it is still lower than the pre- 

 ceding one but not quite as broad. 



The internal suture (pi. VII, fig. 31, 32) is very characteristic. It 

 shows a broad antisiphonal lobe divided into three parts by two slender 

 and long saddles. The middle branch is lanceolate and symmetrical, 

 ending in a sharp point, and is much deeper than the two lateral 

 branches. These are asymmetrical, ending in a point which is near 

 the inner side of the branch. The two saddles which divide the anti- 

 siphonal lobe are long and slender, rounded, entire, somewhat con- 

 stricted above their base and leaning a little toward the central branch 

 lobe. The first lateral lobe is much narrower than th'e antisiphonal 

 one, but broader than each of its branches. It is about as deep as the 

 lateral branches, and is asymmetrical and bifid, the outer point being 

 much longer than the inner one. The second lateral lobe is practically 

 syipimetrical and trifid, the middle point being much longer than the 



