NUCULA. 151 



B. Inner margin plain. 

 4. N. te'nuis*, Montagu. 



Area tenuis, Mont. Test. Brit. Suppl. p. 56, tab. 29. f. 1. N. tenuis, F. & H. 

 ii. p. 223, pi. xlvii. f. 6, and (animal) pi. P. f. 5. 



Body white : mantle open in front and at the posterior side, 

 with a plain edge : foot white, rather longer and not so decidedly 

 pedunculated as in the other species, nor are the margins of its 

 disk so coarsely serrated, although the crenulations are more 

 numerous. 



Shell obtusely and obliquely triangular, and inclining to a 

 circular form, compressed, thin, glossy : sculpture, only slight 

 and irregular transverse ridges : colour bluish- white under the 

 epidermis, which is yellowish, with a tinge of light brown, 

 highly polished and lustrous, and destitute of microscopical 

 or any other markings : margins truncate at the anterior side, 

 and obtusely angled at the point of junction with the ventral 

 range, rounded and broad in front, and slightly produced or 

 wedge-shaped on the posterior side : beaks blunt, and scarcely 

 prominent, not much recurved: lunule comparatively small 

 but raised, defined by a slight ridge ; ligament strong : carti- 

 lage pear-shaped, contained in a rather large and broad cavity : 

 hinge-line curved, occupying about one-third of the circum- 

 ference of the shell: hinge-plate forming an oblique groove 

 on each side of the beak : teeth long, sharp, and nearly straight, 

 about six on the anterior, and sixteen on the posterior side : 

 inside silvery- white and iridescent, faintly striated length- 

 wise, with the margin somewhat thickened : muscular scars 

 roundish-oval, rather distinct. L. 0-425. B. 0-45. 



Yar. inflata. Shell smaller, more triangular and tumid, 

 with the front or ventral margin less curved : beaks more pro- 

 minent. L. 0*3. B. 0-3. N. inflata, Hancock, in Ann. & Mag. 

 Nat. Hist, xviii. p. 333, pi. v. f. 13, 14. 



Habitat : Sand and mud, in 25-100 fathoms, on the 

 north-east coast of England, every part of Scotland 

 from the Eirth of Forth to Unst, Dublin Bay, and 

 (according to the late Mr. Thompson) the east of Ire- 

 land. It is, however, a local species. Dr. Goodall was 



* Thin. 



