MALACOZOA. TROPIOPODA. LAMELLIDRANCHIATA. 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. Astdrte, 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. I 



3. Astarte sulcdta. 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 multicostdta. 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^A. 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- 

 thercea, a title given to Venus, from the island of Cy thera. 



