ii8 University of Texas Bulletin 



section nearly hemispherical, broader than high. The greatest width 

 lies in the umbilical region, a little above the umbilicus. The height 

 of the whorls increases much more rapidly than the width, as is shown 

 in our table of dimensions. The flanks curve rapidly down to the um- 

 bilicus, which is very small. The outside of the shell does not show 

 any constrictions or varices but on the few moulds collected we observe 

 several deep constrictions, which evidently correspond to the internal 

 varices of the shell. These constrictions are slightly bent backward 

 on the flank and form a deep curve backward on the ventral portion of 

 the shell; this latter curve is much deeper and narrower on the larger 

 specimens than on the small ones. Their number could not be ascer- 

 tained. The body chamber is unknown. 



On most of the specimens the shell is preserved but to it adheres 

 nearly always the inner part of the shell of the next larger whorl so 

 that they show not only the internal ornamentation of the shell but also 

 the internal suture line, which gives the species a very remarkable 

 aspect. Only in some specimens (pi. VI, fig. 39-42) is the external 

 surface of the shell preserved. The ornamentation consists of strong 

 and high spiral ribs separated by wide and flat interstices; we count 

 about thirty-three ribs between the umbilicus and the sipho. On the 

 internal side of the shell the ribs appear as narrow and deep furrows 

 and the interstices as broad and slightly rounded ribs. No lines of 

 growth are visible. 



The septa form a straight line and are widely separated from each 

 other. The external suture (pi. VI, fig. 43-45) consists of the siphonal 

 lobe divided by a median saddle, three lateral and auxiliary lobes and 

 four saddles. Each branch of the siphonal lobe is about as broad as 

 the first lateral lobe but is also a little deeper. The two lateral lobes 

 are of a similar form, being wider in the middle than above, and 

 pointed in the lower part. The first auxiliary lobe is a little wider 

 than the other two and broadens towards the upper part. The three 

 lobes decrease in depth from the first toward the third. The median 

 saddle of, the siphonal lobe is high, slender, constricted near the middle 

 and notched at the top by an indentation. The external and the two 

 lateral saddles are similar in outline but decrease in height from the 

 external toward the second lateral. They are high, slender, entire, 

 rounded at the top and constricted above their base; the first auxiliary 



