THIRD, OB \ EBMICEB \N BRANCH. 139 



tlu- usual .-tout -month whorl of the young of «/< ; Quenstedt places them 



with ■ tin-, we tliiuk. is a mistake, arising inmi not giving proper 



bl to tin- characteristics oi the nealogic sta 

 The presence of tlii- form in the North German basin is worthy of remark, 

 since :t i- a degraded variety. The transitional keelless varieties uniting this 

 species and • would have been considered distinct under the name tortile, 



while the keeled forma would ha\ <• been separated and designated as a distinct 

 -. but for the Tact that similar variations are also represented within two 

 other * and Nodolianum. It is evident from tlii-. that tin- 



ki-rl in I a has not become an hereditary character, but is a morpholi 



equivalent in varieties of different 



Caloceras Liasicum. 



Amm. I. . I. pi. xlviii 



Amm. Liat ■.-. Ho i i:. t • ph. Li i- ' . : en, pi. iii fig 



i Die Amm. Schwab. Jon, p. S I, pi. i. 



Amm. /.i fig 1 



.mi. l.iax Amm . p 



; pi xvi. fig. 1 . 2. 

 WftiOHT, Ibid., pi i 



\ 1 . 1--7. pi xx flg 1 6 



I 



A men in the Tubingen collection, about 100 mm in diameter, 



shows by comparison with D'Orbigny's figure that nronofus, Quenst, is prob- 

 ably identical < in"' specimen al Seraur retained very gibbous sides and broad 

 imeter of I7"> mm., and then formed an elevated abdomen with- 

 true keel as figured by D'Orbigny. Another shell bad reached 

 the <1 mm., but no true keel was formed, though old age began to 



■how it- approach in the obsolescence of the pike. In D'Orbigny's collection 

 very broad forms Btand Bide b} side with the narrow one figured by hiin, 

 which i- identical with - Quensl D'Orbigny's original has the keel as 



developed at a diameter of 100 mm as the broad variety at a diameter of 

 tnparison oi the young with t 1 1 . - young ol bowed that they 



nllied by their development. No constant distinction exists, except 

 that / usually ;i Btouter shell, and has about the same relation to 



that ' forms ol in the Upper Bucklandi l'«'«i have to th< 



in lower b( '■' - work upon tli 



the young, and ( J The keel ap 



in Iii- I ill luit probably full-grown specimen, but no channels 



on. 



Tli' : forms discovered by Neumnyr . ■ i ■ • 1 Wiilinei in 



i Alps enable - the foil 



in - 



