FOURTH, OB < ORONK 1 l: \n BR V N « II. ]>7 



outline. an>l the pilaa are similar. A* a whole these four specimens differ 

 I '11 having a shallower umbilii lewhat 



Br number of whorls in proportion to tl the shell. One specimen 



from - intermediate in characters betweeu the German specimens, and 



the tn v /< var. Gaudryi. The Semur specimens al-<> differ in the depth 



ami groove-like aspect <>t the channels, and the almost sunken aspect <»f the keel 

 Dii the • ists I In- prominence of the genie uhs reminds one <>i the fifth whorl of 



i specimens from Semur have similar Butures. The ventral lobe is deep, 



the superior lateral saddles and lobes very shallow and broad, the inferior lateral 



■addles very prominent, and the inferior lateral lobes ol marginal lobes 



are more evenly distributed than in the German variety. The sutures on the 



'i whorl have an abdominal I * • 1 » « - from one half t<> two fifths longer than 



the superior lateral lobes, and the inferior lateral Baddies exceed the superior 



laterals in the -aim- proportion. l!«>ih in fact approximate to ' s i, var. 



their Butures. In the German specimens the lobes and Baddies show 



about the same genera] proportions, though the inferior lateral Baddies arc much 



broader, and the inferior lateral lobes deeper, and acute instead of obtuse. There 



imeii in Professor Quenstedt'a collection from Bodelshausen 



(No 10673 . which is similar to these, but unfortunately the name of tlii- was 



The keel i- quite prominent at the earliest period observed on the Bret 

 ter of the fourth whorl, but the channels are hardly discernible. At this 

 period the channel ridges are not developed, and the tuherculated genicula 



pun the Bides. When the channel ridges are distinguishable "it the fifth 

 volution, they are continuous. The keel loses its prominence alter the channels 

 i upon the latter part of the fifth, and the early part of the Bixth whorl. 

 The pilaa in the young are more numerous than in the adult. 



The specimen from Semur measured 348 mm. in diameter, and had 



• and a half volutions. The pilaa retained all their adult peculiarities 

 and original sharpness, ami the quadragonal form <d the whorl was also un- 

 channels were, however, broader and shallower than in the adult. 

 The approx form in aspect and characteristics to it- morphoh 



equivalent, Cor. i>ir«. ■-. that only the moat careful Btudj can show them 



tn have been distinct The young "i these two bj quite different at all 



idilj sepai 

 Th J ways the broad abdomen ol - 



tubercles, and the youi lout as in < In the 



I, and 



then • • sided whorl, whereas in this species the developm 



much l PI ite \ 1 1 I in form to 



when quite small (Plate IV. Fig. 9 I enicuke usuall) cut up the channel 

 : 1. though not invariable in the s| 



oralis 'i the 



