76 



XL. Delphimda. A subdiscoidal, or short conical, solid, pearly, um- 

 bilicated univalve, with rather rough turns. The opening round ; the 

 margin circular and uninterrupted. 



This genus is formed of shells, which were included by Linnaeus in his 

 genus Turbo: a genus which he formed merely on the character of the com- 

 plete roundish opening of the shell. Lamarck, for the sake of greater ac- 

 curacy of distinction, has separated from this genus those shells, in which 

 the two edges of the opening are circularly united ; and has left to the 

 genus Turbo only those sea shells, which, possessing a rounded opening, 

 have the two edges of the opening constantly disjoined near the colu- 

 mella. With the shells which have been thus withdrawn from the genus 

 Turbo, he thought it necessary to form the genera turritella, scalaria, pupa, 

 and cydostoma. But even thus, some confusion would exist ; since 

 cydostoma would contain both sea shells and land shells. To avoid this, 

 the present genus is formed for the reception of the sea cydostoma, whilst 

 the land cydostoma are all reserved for the genus so named. In the del- 

 phinulse the edge of the opening is not reflected outwardly, nor is the 

 point of the columella visible. 



Turbo testa umbillcata convexa, aufractibus, terctibus striatis : striis crenu- 

 latis inaqualibus. Apertura omnino orbicularis. Foss. Hant. Tab. i. Fig. 7 

 and 8, may be taken, as exemplifying this genus. I am not acquainted 

 with another British fossil of this genus; whilst, of those found in the 

 environs of Paris, Lamarck enumerates eight species : D. calcar, D. lima,. 

 D. conica, D. turbinoides, D. marginata, D. striata, D. sulcata, D. canalifera. 



With respect to the fossil shells to which I now call your attention, I 

 must acknowledge my inability to determine precisely in what genus 

 they should be placed. Their characters, however, approaching the 

 nearest to those of this genus, I have placed them here, until more 

 illustrative specimens have pointed out for them a more appropriate 

 situation. 



Plate VI. Fig. 1, is the upper side, and Fig. 3, the under side, of a 

 limestone fossil, not very uncommon, I believe, in the neighbourhood of 



