400 MOLLUSCA. ARCADE. Pectunculus, 



upon the surface ; anterior margin straight, prominent near the hinge. — • 

 Sower. Min. Conch, t. ccvii. f. 2. — In Green Sand. 



6. C elongata Elongated, subcylindrical, finely striated ; anteriorly 



pointed; posterior side very short.— Somffer. Min. Conch, t. ccccxlvii. f. 1 



Inferior Oolite. 



7- C. costellala — Transversely oblong, gibbose, longitudinally striated ; an- 

 terior lobe wing-shaped, ribbed ; posterior side rounded, ribbed ; beaks in- 

 curved, distant from each other — Sower. Min. Conch, t. ccccxlvii. f. 2. — Green 

 Sand. 



8. C. minuta — Elongated-ovate, convex, striated, anteriorly submucrona- 

 ted ; anterior lobe small, separated by a keel ; beaks nearly close — Sower. 

 Min. Conch, t. ccccxlvii. f. 3 — Oolite. 



9. C. rudis — Transversely oblong, convex, rugged, and longitudinally rib- 

 bed ; beaks incurved, nearly close together ; anterior lobe not denned. — 

 Sower. Min. Conch, t. ccccxlvii. f. 4~-Oolite. 



Gen. XCIX. PECTUNCULUS.— Shell orbicular, subequi- 

 lateral ; hinge line semicircular, the teeth in the middle ob- 

 solete ; ligament external. 



405. P. piloses. — Shell tumid, nearly equilateral, with nu- 

 merous longitudinal stria? and transverse lines of growth. 



P. ingens, List. Conch, t. ccxlvii. f. 82 — Arca'pilosa, Linn. Syst. i. 1143. 

 Area Glycymeris, Penn. Brit. Zool. iv. 98, t. lvii. f. 58 — A. pilosa, 

 Mont. Test. Brit. 137 — Pect. Glycymeris, pilosus, and undatus, Turt. 

 Biv. Brit. 171 Inhabits Weep water. 



Diameter upwards of 2 inches, covered with a thick, brown, pilose cuticle, 

 underneath which the shell is whitish, with brown interrupted stripes, either 

 transverse or longitudinal ; beaks tumid, and slightly recurved ; inner mar- 

 gin notched — This species differs from the P. glycymeris of Lamark in the 

 absence of the longitudinal ribs, with their intermediate striae. 



406. P. decussatus. — " Shell orbicular, flat, decussate, with 

 clouded coloured marks." 



Turt. Biv. Brit. 173, t. xii. f. o — British Channel. 



" Shell an inch in diameter, quite orbicular, flattish, with numerous fine 

 raised decussate lines, which are clothed with a silky brown pile ; colour 

 yellowish-white, with purple and crimson clouded patches, which are often 

 disposed in zigzag angles, giving the shell a beautifully marked appearance : 

 inside fglossy white, with frequently a dark red blotch near the centre ; the 

 margin very strongly serrate." — Turton. 



407. P. nimimarius. — " Shell lenticular, with the beaks per- 

 manent, covered with numerous rounded red dots." 



P. exiguus, List. Conch, t. cexxxix. f. 81. Turt. Biv. Brit. 174. t. xii. 

 f. 6 — Torbay and British Channel. 



" Shell about half an inch in diameter, rather convex, very finely decus- 

 sate, yellowish white, or cream colour, with numerous round red dots, which 

 very rarely become confluent about the margin, and form short lines ; beaks 

 tumid and prominent, causing the margin on each side of them to appear a 

 little projecting, or, as it were, slightly eared like a pecten." — Turton. 



