184 University of Texas Bulletin 



Medlicottia n. sp. 

 The shell is discoidal, very involute, flattened on the flanks and has 

 a deep furrow on the venter. The cross-section of the whorl is sagitti- 

 -form but truncated above and notched by the furrow, much higher 

 than broad, the greatest width existing at about two-thirds of the 

 height of the flank, counted from the umbilical border. On these lower 

 two-thirds the flanks are nearly flat while in the upper third, the shell 

 curves itself slightly toward the venter. On the venter are two lateral 

 keels separated by a deep furrow ; these keels are not sharp but rather 

 strongly beaded; the nodules are rounded and separated from each 

 other by narrow, nearly lineal, shallow depressions; the nodules are 

 wider across the keel than in the direction of the spiral line. They 

 occupy the same height on both keels and do not alternate as in cer- 

 tain stages of growth of M. artiensis. The umbilicus is very narrow, 

 its border is rounded, the umbilical wall seem3 to be very steep. All 

 the specimens are casts and no ornamentation could be observed on the 

 flanks, only on the venter the shell is sometimes preserved and the 

 nodules show in it as well as on the cast. 



The suture is surprisingly simple, the septa stand very near each 

 other, the points of the saddles touching the base of those of the next 

 younger line. 



The external lobe is apparently clearly bifid, narrow but not very 

 deep, compared with other species of Medlicottia. The first lateral 

 lobe is less deep than the second one and bifid, the branch nearer to 

 the umbilicus being a little stouter than the one nearer to the venter. 

 The second lateral lobe is similarto the first but much deeper. Neither 

 is entirely symmetrical. The seven auxiliary lobes now following are 

 much shallower than the lateral lobes and only the first three are still 

 clearly bifid, while the rest are simply funnel-shaped. 



The external saddle is divided in two very unequal branches by a 

 bifid adventive lobe "A" ; the branch on the venter and the contiguous 

 part of the flank which, with Noetling, we shall call Esi, is much 

 higher and more complicate than the one nearer the umbilicus, Esa. 

 The former one is notched on its ventral flank by only one rudimentary 

 lobe, and on the flank toward the umbilicus by two considerably deeper 

 rudimentary lobes, which cause two rather long and not quite parallel 

 rudimentary saddles. The adventive lobe "A' is bifid and symmetri- 



