BEEK M AN T OWN AND CHAZY FORMATIONS OF CHAM PLAIN BASIN 457 



Since Schroder has shown that Whitfield based his description 

 partly upon the specimens which are now the types of E . ro- 

 tund u s , we must accept Schroder's diagnosis, based on 

 Whitfield's first figure, as the only valid one. 



Since however Schroder had not the 

 type specimen in hand and Whitfield lias 

 figured neither longitudinal nor transverse 

 sections of the type it is evident that that 

 portion of Schroder's diagnosis which gives 

 the interior characters can not be reliable. 

 It is clearly copied from Whitfield's de- 

 scription, which in its turn refers again to 

 the smaller specimen, or the present E. 

 rotundus. It is probably on this ac- 

 count that Hyatt queries the correctness of 

 Schroder's diagnosis [1894, p. 442]. Be- 

 sides the internal characters, the material 

 from Yalcour furnishes other additional 

 diagnostic characters not obtainable from 

 the type specimen. We have for these rea- 

 sons and also because Schroder's diagnosis 

 is probably not everywhere readily acces- 

 sible inserted here a full description of the 

 species drawn from Professor Wmitfield's 

 specimen, and from our material obtained 

 at Yalcour. 



Description. Conch a rather closely 

 coiled nautilicone up to gerontic age, when 

 the living chamber becomes free, but does 

 not straighten and only unfolds into an 

 arc with a larger radius, 4-5 volutions, giv- 

 ing the conch a diameter of 170 mm. Yolu- 

 tions slightly compressed, elliptic in section 

 in the ephebic stage and subcircular in the 

 nepionic and neanic stages [see text fig. 21] ; ratio of hight to width 

 of volution where the latter has a hight of 27 mm approximately as 

 9:8 and where it has a hight of 40 mm as 10:8. Xo lateral zones 

 differentiated ; a ventral zone indicated by a slight flattening ; the 

 impressed (dorsal) zone slight but continuous upon the free geron- 

 tic volution ("persistent impressed zone"). Growth of conch 

 quite rapid, the shell doubling in hight and width within the length 



/ 



Fisr 



Knrystomites k e 1 - 

 loggi Whitf. (sp.' trans- 

 verse section. X. aural size 



