113 



ornamentation. On the last whorl the three keels with their 

 rows of nodes are distinctly seen ; on the superior keel the nodes 

 are more strongly developed than on the others ; on the lowest keel 

 they are least developed. The distance between the lowest and 

 the middle keel is somewhat less than between the middle and 

 the superior keel. In this specimen it is moreover seen that the 

 inner lip is broadly expanded, and very thick. The wing at any 

 rate reached to the fourth whorl from the base of the shell ; 

 whether it reached higher up cannot be seen, as the shell is 

 broken here. The prolonged part of the wing is missing in 

 this specimen. 



From the Coeloma-bed we have likewise a specimen of this 

 species with the shell partly preserved. From the cast it is seen 

 that on the last whorl the superior row of nodes is well deve- 

 loped; the middle keel is only faintly indicated, while nothing 

 is left of the lowest keel. The slanting transverse ribs, which 

 are characteristic for this species, are present on the middle 

 whorls, and have left their impressions on the cast. Of the 

 shell itself the wing is preserved , but is somewhat decayed 

 on the surface. It is of about the same shape as in Beyrich: 

 pi. 11, fig. 3; but the part rising along the spire seems to 

 have been very narrow. On the surface of the wing the three 

 stubby keels are seen; two of these are about equally strongly 

 developed, while the lowest is very sligthly developed. The 

 wing almost reached the apex. The aperture is considerably 

 contracted. 



This form greatly resembles the species which Gardner ^) 

 has described under the name of Ä. Margerini de Koninck. 



According to Gardner however the wing of this form only 

 reaches the last whorl but one or the last but three, while as 

 mentioned, in the Greenland form it almost reaches the apex. 



^) J. Starkie Gardner: British eocene Aporrhaidae. — Geol. Magazine. 

 New Series, Decade III, Volume I. London 1884. p. 532, pi. 17. figs. 

 7—8. 



