S \ OF THE RHONE BASIN. 106 



- indicates thai the bucklandian horizon of this basin represents the 

 Lower Bucklandi beds of other bat 



Dumortier divided hi- tone <»i Amm, oxyitoiua into four beds, distinguished 

 by their bunas. 



The •• Davidsoni bed " should have been called Strinries bed, Bince b - I 



is identical wil A The list of sp< not enable 



one i»> synchronize these beds with the Tuberculatum beds <>i Seraur or other 

 . nor <!<> they -how that it is equivalent to any bed above the Upper 

 Bucklandi beds. 



The Stellaris bed <>( Dumortier contains, besides the Bpecies mentioned in the 

 table, I / : Deroceras, and Amm. Birch,* form of Microdo- 



ts; both of these, therefore, belong t<> ;i family distinct from the Ai 

 The presence of />'</,/. B r, and obtusion bdow that this, and not the so 



called Davidsoni bed, i> the equivalent <»t' the bed immediately above the Upper 

 Bucklandi beds at Semur. This result confirms our opinion that the David- 

 soni bed of Dumortier should be called the Upper Bucklandi bed. 



Dumortier's Planicosta bed contains ' . : which i- identical with A I. 



i (i; and this seems ti> settle the geological [>"-iti<>n of this important bj 



Alum. seems t" be an abnormal or diseased Am. misera . PellaU is 



a young form of ' iUa* if one can trust the ospi 



the inner umbilical pike, is a diseased form of Col. rarico&tatum. Ii appears from 

 the figure t>> be similar t<> the deformed Ahnm. longidomus asger « > i Quenstedt, 

 other similar pathological forms, in which the keel and channels have been Buper- 

 _mwtli by ]>il;»' crossing the abdomen. 

 I i' WXI Fig 9—13) is the same as the Johnstonian variety of 



' / P •■■ X X X I X i- the equivalent <>f the young i 



Plate XXXI Fig. '■'>. \\ may be related t>» Arn.ful 

 The umbilicus, Butui neral aspect of the last indicate that ii is a form 



keeled and channelled form of 

 Arnioceras, with distorted pike. 



/ ' • all varieties of our /' 



and belong to a family distinct from the Arietidsa 



The three upper beds <it Dumortier are apparently the equivalents "i the 

 Birchii or Tuberculatus beds in the table "i the Cdte d'Or b 



The notable facts brought out by thi> table are as follows Then 

 irity in tin- distribution of the schlotbeimian series Bimilar t<> that in the 

 I ' fully repn -•■!! tt«l in the lower beds, and is 



equally deficient in the Bucklandi zone. It is represented by a full lis! 

 in the highest beds, with the i, which is absent I 



however, is more fully represented, and ( 

 niiinl' than in any < <t Ii»t lamia. The arnioceran series is not bo 



fully i ted in the Bucklandi zone, but it is notably richer in forms in the 



Is than in an. I is well represented in the 



i i 



n 



