MALACOZOA. TROPIOPODA. LAMELLILRANCHIATA. 211 



epidermis dusky, reddish, or yellowish. Named from 

 its being found in Iceland. 



Genus 3. Astarte. — Shell roundish or elliptical, com- 

 pressed or moderately convex, with a persistent epider- 

 mis, one valve with a thick tooth and two pits, the other 

 with two thick teeth and a triangular pit ; the pallial 

 impression entire. Astarte, a name of Venus. Sowerby. 



1. Astarte Danmoniensis. — Shell rotundato-trigonal 

 or suborbicular, thick, with concentric convex ridges, 

 narrower than their interstices, the margin crenate within. 

 Danmonia, Devonshire. 



2. Astarte Scdtica. — Shell rotundato-trigonal or sub- 

 orbicular, thick, with concentric convex ridges, nar- 

 rower than their interstices, the margin plain within. 

 Scoticus, inhabiting Scotland. 



3. Astarte sulcata. — Shell rotundato-trigonal, convex, 

 subangulated behind, the anterior end longer, very thick, 

 with concentric convex ridges, of the same breadth as 

 the interstices, the margin crenate within. Sulcdtus, 

 furrowed. 



4. Astarte elliptica. — Shell ovato-elliptical, compress- 

 ed, the anterior end much shorter, moderately thick, 

 with broad little elevated concentric ridges, becoming ob- 

 solete at the two ends, the margin plain. Named from 

 its elliptical form. 



5. Astarte multicostata. — Shell trigonal, moderately 

 convex, the anterior end slightly longer, thick, with 

 about forty regular concentric convex ridges, the margin 

 plain. Named from its numerous ribs. 



6. Astarte compressa. — Shell ovato-trigonal, com- 

 pressed, the anterior end shorter, moderately thick, with 

 irregular flattened ridges and shallow grooves, obliterated 

 toward the margins, which are plain. Compressus, 

 flattened vertically. 



Genus 4. Cyther.ea. — Shell suborbicular, moderately 

 convex, concentrically striated ; umbones small ; three 

 divergent teeth in one valve, four in the other ; pallial 

 impression invaded by an oblique tapering sinus. Cy- 

 tkercea, a title given to Venus, from the island of Cythera. 



