NUCULA. 221 



inch in breadth. When of these dimensions, the front 

 declination is so abrupt (and almost rectilinear) that the 

 beaks are all but perfectly terminal. 



The remark made respecting the animal of Nacula 

 nitida equally applies to this. 



This species is probably widely distributed, but having 

 been usually confounded with nucleus, it is difficult to ascer- 

 tain its precise range. Certain localities are South Devon, 

 Torbay (Alder and S. H). Milford Haven, in ten 

 fathoms, always in separate parts of the bay from nucleus 

 (M' Andrew and E. F.) ; Lundy Island, seven to twenty- 

 five fathoms in sandy-gravel (M'Andrew). Lamlash, 

 Arran (Alder) ; and, probably, Exmouth (Clark). Mr. 

 M'Andrew has taken this form at Gibraltar. 



N. decussata, Sowerby. 



Solid, decussated ; hinder dorsal area barred with wavy piri- 

 form wrinkles. 



Plate XLVII.fig. 1,2, 3. 



Nucida decussata, Sowerby, Concholog. Illust. Nucula, No. 27, fig. 18. — Hanl. 

 Recent Shells, vol. i. suppl. pi. 20, f. 8. 

 „ sulcata, Bronn, Italiens Tertiar-gebild. p. 109 (inadequately). — 

 Philippi, Moll. Sicil. vol. ii. p. 45; Wiegmann's Archiv. 

 Naturg. 1845, p. 192, pi. 7, £ 24, 25. 

 „ Polii, Philippi, Moll. Sicil. vol. i. p. 63, pi. 5, f. 10. — Jeffreys, Ann. 

 Nat. Hist. vol. xix. p. 313. 



The general aspect of this shell is not unlike that of 

 nucleus, to which its outline is very similar. It resembles 

 that shell much more nearly than it does either nitida 

 or radiata, owing to the existence of an anterior side, the 

 beaks being far less nearly terminal in the present than in 

 the three preceding species. It is. however, slightly more 



