DIFFERENT] \l. < II \l: \< TERIS1 SI 



took place independently of increase in the breadth of the whorl by growth, or 

 of increase in the involution of the auccessh 



The radical Bpecies of the laqueum Bubseries Bhowed a completely arietian 

 form of whorl. This appears in Cul. I- [uadragonal in section, with a 



keel, faint channels, and straight pita, tnberculated in one variety. This form 

 lated in ' ol the Upper Bucklandi bed; the keel and ribs 



bowever, somewhat more highly developed in one variety of Col. re 

 tnti'ii). The deep narrow abdominal lobe, also a peculiar arietian characteristic, 

 . ; 1 1 1 1 was perpetuated in raricostatum ; it was repro- 

 : it .1 very early age in the last species, and in Cal l> The peculiar- 



.lit or curved, fold-like, and crowded pilse are differentials of 

 importance, which correlate with the other immature transitional characteristics 

 of till- - described in the chapter on Descriptions of Genera 



and Species discovered in the Northeastern Alps shows that highly compn 

 forma with acute abdomens occurred also in thi> genus. ( I agnolcd had 

 a tendency towards increase of involution, though this Bhell, and even the 

 •in ■ form abnormHobatum, must still !»• classed as discoidal. 

 In the radical Bpecies of Vermiceras, Ver. spi . the whorl became 



quadragonal with flattened sidesand abdomen, channels, and pilaa with arietian 

 ilae. These charai I ere maintained throughout the Beries, be- 



coming more intense in P ' hearty and inherited at a very early nealogic 

 in Ver. oph Die shells remained discoidal, however, as in Caloceras, 



even in the largest specimens. Looking back, we Bee that the radical Bpecies, 

 ( ./ .and Ver. •/■>' formed a series of proximate 



i ils, in which there was a regular gradation in the intensity of expression of 



tin- different characters after they were once in trod u I, culminating in tin' 



quadragonal form and arietian Butures of tpiraiissimum. We could, therefore, 



te these three form- in a distinct Beries, and they 



would then be related bj - parallel with thos< mrring in either Calo- 



\ though corn] d solely of radical Bpecies. This is possible 



the discoidal forms of the species of the vermiceran branch of tin- 

 "k. all of which have numerous whorls, and retain tin- very long living 



• least one volution in length, of the Pailoceran St<><-k. 



The differentials of the L Stock had a more abrupt beginning, the transi- 

 /• to the first form, .1 or the lower varieties 



/'"in. having I n less complete, and tin' forma separated by a 



of time. There w much quicker transition from the 



helmet-shaped whorl to the quadragonal. This took place in the first spei 

 tin- ti: ind 1 1 » i — radical, whether the one or the other of the two men- 



tioned, i- keeled in adults. In .1- ilxo. 'In- pilaa assumed in most 



• peculiar straight, trenchant aspect, and the prominent and square 



ImI nd 



the keellesa, smooth form of /' so long in 



the growth of some individuals that it !>• 



in oth important, it is always found as a 



n 



