58 University of Texas Bulletin 



inner, and those toward the umbihcus as the outer ones). It is not 

 nearly so deep as the siphonal lobe, but deeper than the second lateral 

 one. This branch is leaning toward the outside; i. e., the bottom is 

 nearer to the sipho than its top. It is separated from the next second- 

 ary lobe by a relatively high secondary saddle which leans over 

 to the outside. It is entire and rounded at the top. The 

 other three secondary lobes are very small and shallow and 

 together with the two saddles which separate them, resemble the 

 teeth of a saw. The second lateral lobe is nearly symmetrical, tongue- 

 shaped, narrower at the top than below the middle, and ending in a 

 point. The first auxiliary lobe is asymmetrical and curved with the 

 convexity toward the inner side, pointed at the lower end. The second 

 and third auxiliary lobes are again symmetrical, pointed, narrower 

 at the upper part than below the middle. The fourth and fifth aux- 

 iliary lobes are symmetrical, pointed, but about equally wide in their 

 upper half. The fifth auxiliary lobe lies near the umbilical border and 

 there follow still two more lobes on the umbilical border and wall. 

 The sixth is similar to the fifth, but smaller; while the seventh is ex- 

 tremely small and rather like an indentation. 



The saddles are all entire and rounded, but differ in height. The ex- 

 ternal saddle is moderately high and leans over toward the sipho. It 

 is not constricted. All the lateral saddles on the flank are of the same 

 shape; i. e., rounded at the top and more or less constricted above the 

 base. The first and second lateral saddles are higher than the external 

 and very similar to each other in width and length. The first auxiliary 

 is considerably shorter. From the first to the fifth (on the umbilical 

 shoulder) the saddles decrease steadily in length and width, but all are 

 more or less of the same shape. The sixth and seventh auxiliary sad- 

 dles, which lie on the umbilical wall, reach with their top to the contin- 

 uation of the line formed by the upper end of the preceding saddles, 

 but their base lits much higher than that of the saddles on the flank. 



The internal sutures could be studied only in a specimen whose 

 furrow on the ventral part is not yet developed, but in an adult whorl 

 the general outline of the internal suture is visible and it does not 

 materially differ from the one we are about to describe. 



The internal suture shows a very deep antisiphonal lobe of lance- 

 olate form, much narrower at the top than below the middle. The 



