LUCINA. 239 



to each side. In the present species the striae run ob- 

 liquely from one side to the other, curling upwards at 

 each end. L. divaricatus is very convex, white with a 

 tinge of pale yellow, and rather glossy, while L. pisi- 

 f or mis is compressed, and has a rosy tinge and dull hue. 

 The markings on the latter shell are such as may be seen 

 on the tip of a finger, and from these the names digitaria 

 and digitalis have been derived. It occurs in the Red and 

 Coralline Crag. In consequence of the anterior mus- 

 cular impression being simple, Searles Wood placed this 

 shell provisionally in Astarte ; and Deshayes has lately 

 formed out of this and other allied fossil species the 

 genus Woo dia, a just compliment to our distinguished 

 paleontologist. 



Genus II. LUCI'NA* Bruguiere. PI. V. f. 5. 



Body somewhat compressed: mantle having the margin 

 waved : incurrent as well as excurrent tube sessile : foot tongue - 

 shaped. 



Shell rather inequilateral, concentrically ridged: lunule 

 long and well denned : ligament for the most part external : 

 teeth, one or two cardinals in the right, and always two in the 

 left valve, one of which latter is often cloven ; laterals long 

 and laminar : inside chalky and pit-marked. 



Although this genus has been divided, it must be 

 borne in mind that very nearly three-fourths of a cen- 

 tury have elapsed since it was first instituted. The 

 progress of conchological discovery has been unusually 

 rapid during the last twenty years, owing in a great 

 measure to the impulse and encouragement given to the 

 study of the Mollusca by publications specially devoted 

 to it, as the f Zeitschrift fur Malakozoologie/ f Malako- 

 zoologische Blatter/ and 'Journal de Conchyliologie/ 



* An epithet of Juno. 



