78 University of Texas Bulletin 



saddles, but smaller; the adventive lobe A, which divides the two 

 branches is deep, and parallel to the branch Esi. The lateral saddles 

 Lx and L2 are strongly trilobate ; that is, while their general form could 

 be called tongue-shaped, they show near the middle two lateral pro- 

 tuberances, of which those directed toward the second lateral lobe are 

 pointed downward, while those directed toward the first lateral and 

 the first auxiliary lobes are pointed upward. The saddles are some- 

 what constricted below these protuberances. The second lateral 

 saddle is higher than the first one. Of the ten auxiliary saddles the 

 first eight resemble in shape the lateral saddles. Their length and the 

 size of the lateral protuberances decrease rapidly while the width does 

 not change materially, which gives the last of them a stouter form than 

 the first ones show. The ninth and tenth auxiliary saddles are simple 

 and rounded. The tenth saddle lies on the umbilical border. 



In smaller specimens the sutures do not dififer essentially. The num- 

 ber of rudimentary adventive lobes on the siphonal branch of the exter- 

 nal saddle is reduced to seven, and the number of auxiliary lobes de- 

 creases ; but the shape of the saddles and lobes, and especially of the ex- 

 ternal saddle, and its dividing adventive lobe A, does not change 

 materially. 



The internal suture could be seen only on a small specimen (III of 

 our list of dimensions), but it belongs really to the next larger whorl 

 which should have a diameter of at least 40 mm. As internal sutures 

 up to now have not been found in any Medlicottia it is perhaps well 

 worth while to describe these (pi. I, fig. 49, 50). 



The antisiphonal lobe is clearly bifid, a short triangular median 

 saddle causing the division in two points. The lobe is relatively broad 

 and occupies nearly the whole breadth of the venter of the next smaller 

 whorl; it is wider above than below. The first lateral lobe is almost 

 as deep as the antisiphonal one ; it is narrower at the top than near the 

 bottom, and is bifid, the two points being divided by a very low saddle. 

 The second lateral lobe is similar in general shape to the first one, i)Ut 

 it is shorter and the dividing saddle between the points is still lower. 

 The auxiliary lobes, five in number, are all simple and rounded at the 

 bottom ; they decrease gradually in depth. 



The internal saddle is high, slender, and somewhat club-shaped. 

 The first and second lateral saddles are a little higher than the internal 



