FOURTH, OK I OROXIi i:i: VN |.|; \\< II |g] 



\ urination and .11 specimens in 



■ii of Comparative Zoology baa shown thai the average length of the 



abdominal lobe for nealogic and adull Bhella one third longer 



than the superior laterals. The sutures also vary from the comparatively simple 



solid looking and very slightly indented ctreme 



forma figured in our plates and by Quensb 



\ u C. 



Plata i\ ii. in i 



Iii this variety the channels are slower in reaching their full development, and 

 the pilae are no! so prominent, bul are more numerous and conform more closely 

 tn the shape of tin- whorl. The whorl is altogether flatter, and incn 

 what faster by growth than in vain B The channels are hardly perceptible 

 on the fourth volution, and in consequence of the smaller Bize and want of prom- 

 inence in the genicular the abdomen baa at the same time more prominence than 



are i less variable. Thus individual 



\ in -wine characters, or varietj B in i 

 riety C, Plate IV, I _• 15, 16, - nile characters begin t<> be 

 ent upon the second quarter of the ninth whorl. Thepihe are -till slightly 

 minted, th" abdomen though much narrowed is >till comparatively broad. 

 In a specimen "t variety B, at same time th<- abdomen bad become narrow, tin- 

 pike bad l"«t not only tin- tubercles, but also the genicular, being in their - 

 \ ecimen in the Museum of Stuttgnrdt, from 

 ng 140 mm. in diameter, Bhowed more pronounced Benility. The 

 J\ convergent, tlie pilae obsolescing, the abdomen elevated, 

 ; i the channels and keel were not much changed. In another of the Bame 

 ter the channels were obsolete, the keel n h>\\ broad ridge, the pilaj n duced 

 nl lateral folds, and the sides verj convergent In the ' imens 



.' if the figures are accurate, the keel, channels, and 1 

 itent. 

 In the M I - fine suite of specimens nam< ' 



not show senile decline as early as is usual in this 

 1 Ine at the diami II retained the pilae and the chan- 



ii the abdomen had become much elevated. This spocinv 



i sal diameter w i than 



luminal. 



to be identical with thU i nd the more < 



red "ii PI ntermediate between mj I 



1 • not remember hn\ in 

 mentioned in m) n< 



1 An 



