DTJNDRT GASTEROPODA. 17 



Syn? 1842 Melania coarctata, Desl. Mem. Soc. Linn. N'orm. 



YII. pi. 12, fig. 13, p. 227. 

 Syn? 1854 Chemnitzia coarctata, D'Orb, Pal. fr. Terr. jur. 2 



pi. 240, fig. 1—3, 

 Length, 65 — 85 mm. 



It appears almost hopeless, as Deslongchamps says, to attempt 

 specific divisions to this genus. However, under the above name 

 I would include a group of forms characterized by the wider 

 sutures in the older whorls, each whorl being depressed at the 

 junction; by more wavy lines of growth, and tendency to 

 incipient tubercles on the last whorl. But all of these characters 

 vary so in diff'erent individuals, and even in younger and older 

 parts of the same specimen, that the only character I find left to 

 rely upon in distinguishing it from the preceding species is the 

 absence of punctce. 



None of our shells show the epidermal colours. I should look 

 upon these as most important, and doubt D'Orbigny being right 

 in joining C. turris to C. coarctata, Desl. 



There are six specimens in the Museum. 



Locality — Dundry. Inf. Ool. 



CHEMNITZIA HEDDINGTONENSIS, Sowerby. 



1813 Melania Heddingtonensis, Sow. Min. Conch, pi. 



39, outer figures. 



1850 Chemnitzia Heddingtonensis, D'Orb. Pal. fr. Terr. 



jur. 2. pL 244, p. 56. 



A specimen which would be six inches long if complete, cannot 

 be distinguished from Coralline Oolite forms. "We therefore 

 place it under this name : for to restrict the appellation to 

 forms found in the Coralline Oolite alone, would seem to us to 

 be reasoning in a vicious circle. 



