146 MALACOZOA. GASTEROPODA. PECTINIBRANCHlATA. 



Fergus ; and in October by me, in abundance on fuci on the 

 rocky coast of Kincardineshire. 



Nerita pallidula. Mont. Test. Brit. 468. — Nerita pallidula. Flem. 

 Brit. Anim. 320. — Lacuna pallidula. Turton, Zool. Journ. iii. 190. 

 ■ — Lacuna pallidula. Jolmst. Berw. Trans, iii. 270. 



4. Lacuna sulcata. Glossy Lacuna. 



Shell subglobose, broader than long, rather thin, semitrans- 

 parent, of three-and-a-half rapidly increasing, convex whorls ; 

 the spire very short, obtuse, the suture moderately distinct, the 

 last whorl very large, glossy, smooth, but with oblique growth- 

 lines at intervals ; the mouth circular, when considered as 

 bounded on the left by the ridge margining the broad concave 

 striated pillar groove, or semicircular if the nearly straight 

 margin of the columella be taken as its limit ; the colom grey- 

 ish-white, with a slight tinge of red near the outer lip. Dia- 

 meter nearly a twelfth and a-half. 



The specimen described is considerably worn, and damaged 

 in the outer lip. It was found by me in shell sand, on the 

 beach between the Dee and the Don. This species approaches 

 to Natica, as much as the last to Sigaretus or Velutina. 



Nerita sulcata. Turt. Conch. Diet. 124. f. 56, 57. — Natica sul- 

 cata. Flem. Brit. Anim. 320. — Nerita glabrissimus ! Brown, Wern. 

 Mem. ii. 532. PI. 24. f. 12. 



Genus 8. Rissoa. 



Animal elongated, spiral; with the head proboscidi- 

 form, the mouth somewhat prolonged ; the tentacula 

 subulate, with the eyes on a small prominence near their 

 base externally ; the foot oval or elliptical. 



Shell conical, with the spire elongated, the apex mam- 

 milliform; the whorls generally convex, the suture dis- 

 tinct ; the aperture roundish, ovate, or pyrate, with the 

 anterior end rounded, the posterior acute, the peristome 

 complete. Operculum roundish, oval or pyrate, spirally 

 marked, thin and horny. 



The species are all diminutive, the largest of those 

 occurring on our coasts not exceeding a third of an inch 

 in length, and the smallest being scarcely a twenty- 

 fourth. They are phytophagous, and reside among 

 fuci, in clefts of rocks, on stones, or on mud or sand ; 



