62 ANNALS NEW YORK ACADEMY OF SCIENCES 



The aperture is quadrangular, with short, widely open siphonal canal. 

 The callus of the inner lip is thick and broad. The outer lip is strongly 

 sinuous. 



Horizon and localities : Sables Moyens. La Cliapelle, Le Guepelle and 

 other localities in the Paris Basin. 



No. 20153, Columbia University collection. 



Eemarks : Were it not for the old-age features present on the later 

 part of the body whorl, this variety might be taken for the young of the 

 type species mentioned below, but the shell appears in all ways like a full- 

 grown individual, with a length only about half that of P. cordieri. 



The development of this form is closely similar to that of P. lamarcki, 

 and the adult differs but slightly in general appearance. It is, however, 

 larger, has a wider apical angle and lacks the extremely fine spirals cov- 

 ering the surface between the nodes as in P. lamarcki. 



Potamides cordieri Dcshaycs 



1824. Cerithium cordieri Deshayes, Desc. des coquilles foss. des environs de 



Paris. II, 338, pi. 52, figs. 14, 15. 

 1866. Cerithium cordieri Deshayes, Desc. des animaux sans vert, decouverts 



dans le bassin de Paris. Ill, 137. 

 1906. Ptychopotamides cordieri Cossmann, Essais de Paleoconch. Comp. VII, 



108. 



Measurements : Length, 60 mm. ; greatest diameter, 20 mm. ; apical angle, 

 23.5° ; sutural angle, 90°. 



The only specimen of this species available for study is broken at the 

 apex, but enough remains to show that the development of this shell is 

 like that of the mutation fypum and remains the same in all ways except 

 in the number of spirals on the last two or three volutions. P. cordieri 

 differs from its mutation only in its greater size and in the fact that 

 while P. cordieri mut. typum has only one row of fine nodes intercalated 

 between the coarser ones, the type species has a similar row intercalated 

 between the two lower and also below the lowest of the three rows of 

 strong nodes. The intercalation of tine nodes in the remaining inter- 

 spaces would naturally follow their introduction in one of them, so that 

 the adult P. cordieri constitutes the next step in this line of evolution 

 beyond that of P. cordieri mut. typum. For this reason it would have 

 been more appropriate to consider the mutation typum the type species ; 

 but the name being already established for the larger specimens, it should 

 not be changed. 



Horizon and localities : Sables Moyens. La Chapelle and other localities 

 in the Paris Basin. 



No. 20154, Columbia University collection. 



