158 University of Texas Bulletin 



on the flanks and strongly curved on the venter, with the convexity 

 toward the back, parallel to the constrictions. 



The septa are very near, sometimes almost touching, each other. 



The suture^ (pi. VIII, fig. 4, 7; pi. IX, fig. 10) follows a straight 

 line between the umbilicus and the sipho. The external suture consists 

 of a siphonal lobe divided in two branches by a high median saddle, 

 two lateral lobes and three auxiliary lobes, one external saddle, two 

 lateral and three auxiliary saddles. The siphonal lobe is very broad, 

 shows a number of adventive saddles which augment and become 

 longer with age, and each branch ends in a long sharp point. The 

 first lateral lobe is scarcely deeper than the branches of the siphonal 

 lobe, its walls are deeply scalloped and it ends in a long, sharp point. 

 All the other lobes are similar to this one, only shorter and narrow, 

 decreasing gradually in depth and width toward the umbilicus. The 

 median saddle of the siphonal lobe is high, slender, broader at the bot- 

 tom than at the top and always shows several adventive lobes on both 

 sides. At the top it is notched by a shallow indentation. All the lateral 

 saddles are broad at the base and taper toward the top; they have a 

 number of adventive lobes, which cut deep down near the upper end, 

 but grow gradually shallower toward the base where they are very 

 small. All the saddles end in one phylloid point and nearly all their 

 branches end in a similar way. The external saddle is much higher and 

 broader than any other one ; the lateral and auxiliary saddles are very 

 similar to the external one, but they decrease in height and width 

 gradually toward the umbilicus while at the same time the number 

 of secondary lobes and branches diminishes. 



The internal suture (pi. X, fig. 21) is not entirely known, but the 

 most important part could be uncovered. It consists of a very deep 

 and very narrow antisiphonal lobe of lanceolate form and an undeter- 

 mined number of lateral and auxiliary lobes, a very high internal 

 saddle and an undetermined number of lateral and auxiliary saddles. 

 The long and narrow antisiphonal lobe has several secondary saddles, 

 the longest near the top, the smallest and last below the middle. The 

 internal saddle is very high and very narrow, ending in a phylloid 

 point and possessing several branches that end in a similar manner. 

 It is broader at the base than at the upper end and the secondary 



'Compare also the Appendix to this work, p. 187-190. 



