LEDA. 227 



Jrca caudaia, DoNOV. Brit. Shells, vol. iii. pi. 78. 



Nucula minuta, TvKT. Dithyra Brit. p. 178. — Flem. Brit. Anim. p. 402. — 

 Macgilliv. Moll. Aberd. p. 245. — Brit. Marine Conch, p. 106. 

 — Brown, Illust. Conch. G. B. p. 84, pi. 33, f. 18. — Hanl. 

 Recent Shells, vol. i. p. 1G8, pi. 10, Area, f. 44. — (No, 

 Philippi, Moll. Sicil. ; scarcely Gould, Invert. Massach.). 

 „ rostrata, Macgilliv. Moll. Aberd. p. 245 (not Montagu). 

 Leda mimita (and complanata), Moller, Index Moll. Groenl. p. 17? — King, 

 Ann. Nat. Hist. vol. xviii. p. 240. 

 „ caudata, Lovbn, Index Moll. Skandinav. p. 34 (probably). 



Of the two very distinct forms of this graceful shell, that 

 which we regard as the typical one is oblong-lanceolate in 

 shape, compressed at the longer side, and but little convex 

 at the other ; the central disk is not, however, particularly 

 shallow. The valves are decidedly inequilateral, opaque, 

 moderately strong, and covered with a rather dull epidermis 

 of a yellowish or pale olive-green ; their surface is adorned 

 with numerous regular concentric delicate lyree (or raised 

 strise), which are much narrower than their simple inter- 

 stices. These strise, which vary much in strength and 

 distance, are sometimes much elevated, sometimes rather 

 depressed. This sculpture uninterruptedly and almost 

 evenly occupies the entire exterior, the lunule and the 

 immediate vicinity of the opposite dorsal suture alone ex- 

 cepted. The ventral edge is gently arched at the shorter 

 side, where its ujDward sweep exceeds the descending 

 curve of the dorsal margin, which it surpasses, or at least 

 vies with in convexity ; hence causing the most projecting 

 portion of that side to lie either in the middle or above it, 

 and the tapering but rounded extremity to become occasion- 

 ally a little angulated. It is straighter at the longer side 

 and by its ascent (through trifling), and by its slight sub- 

 terminal retusion, assists the incurved and but moderately 

 sloping dorsal edge in forming a rather long subcentral 

 rostrum, which latter is much attenuated, and somewhat 



