Ill Til. OR KG LSSICERAN BRANCH. 209 



fold-li amnion in 1 1 * . • - They are more acute and about 



equally prominent near the dorsum, and also on the edge of the abdomen, and 

 interrupt (he channel ridges. The earliest period examined was the third 

 quarter of the fifth whorl. One specimen, from Lyme Regis, bad a much nar- 

 rower channel area than in "l" the same age, and the pilaa reached nearly 

 to the 'h«- keel; in another, from Gloucester, the cham better 

 developed, but extremely narrow. This ven on the fifth volution had a 

 ■ I keel, deeper and more distinctly marked channels, and flatter 

 than any variety of I 



One Bpeci n fitom Semur on the second quarter of the sixth whorl had 



from two fifths in three fifths, and saddles from two fifths to 

 one half. 



S nile characteristics begin i<> appear on the latter part of the Beventh whorl. 

 • hv diminish to large folds i>n the second quarter of the eighth whorl, and 

 subsequently disappear altogether. The channels also increase In breadth and 

 diminish in depth. The keel acquires greater prominence in the clino 



m of the shallowness <'t' the channels, but finally becomes 

 The lai. ueii measured had about eight whorls, and the 



diami am. 



- is in the Museum of Stuttgardt These >liells 



triable ages. One from Balingen, about 113 mm. in diam- 



ie entirely Bmooth ; another from Endigen nearly halt' a whorl 



older had »till very prominent pilaa. The peculiar form of the whorl, the deep 



channels and Oat sides, ln»M constantly, however, in these, as well as in a j 



specimen from Balingen, labelled Antm. obtusvs, which also belongs to this si 



beautifully preserved, and ma} be compared with obtvtvm of the same 

 ion. 

 The forms identified by Oppel in the Museum at Munich as I / 



•I with the above. 

 The a<lult specimens <>r one varietj "t '/' ■ i and a lai i 



ther in the Planicosta bed at Lyn i I re quite similar, and 



have led to confusion in names, though the young are distinct, and the pilaa of 

 not bent or curved as in I / i 



ill in hi- identification of I n variety 



:n Ofterdingen, with the English form ol thin - pgured by 



• ;th the young as shown in Wright 

 Another n lien in the resemblances of frn f the 



onsiderobli I 



.-up nt of an outer whorl from Lyme Regis in the Museum of 



1 



ight, the 1 the 



mmon in tl 

 The nbdomen keel and channi 



