78 MOLLUSCA FROM THE CRAG. 



Arca Gaimardii. Desk. Exp. Sci. Algiers Moll., pi. 124, figs. 8 — 11. 



— Quoyii. Payr. Cat. Moll. Cors., p. 62, pi. 1, figs. 40—43, 1826. 



— — Desk. Append, to Lyell's Princ., 1st ed., vol. iii, p. 10, 1833. 



- lactanea. S. Wood. Mag. Nat. Hist., New Series, vol. iv, p. 232, pi. 13, fig. 3, 



1840. 

 _ _ 5. Wood. Catalogue, 1840. 



_ _ Morris. Cat. Brit. Foss., p. 78, 1843. 



— nodulosa? Broc. Conch. Foss. Subap., p. 478, t. ii, fig. 6, a — c, 1814. 



— — ? Dubois. Wolhyn. Podol., p. 64, pi. 7, figs. 21, 22, 1831. 



— striata. Reeve. Conch. Icon. Arca, pi. 17, fig. 121. 



List. Hist. Conch., lib. iii, fig. 69, 1685. 

 Dale. Hist, and Antiq. of Harwich, p. 291, 1730. 

 Adanson. Voy. au Senegal, p. 250, pi. 18, fig. 8, 1757. 

 not Arca lactea, Brander. Foss. Hant., pi. 8, fig. 106. 



Spec. Char. Testa ovato-oblongd, interdum subquadratd, antice rotundatd, postice 

 oblique truncatd ; decussato-striatd ; striis radiantibus eminentioribus ; area cardinali 

 mediocre profunda ; margine ventrali subrectd. 



Shell ovato-oblong, sometimes nearly square, anterior side rounded; posterior 

 obliquely truncated ; covered with striae, crossed by transverse lines of growth ; 

 radiating striae the most prominent ; cardinal area not large, with a rounded or obtuse 

 ridge from the umbo backwards ; ventral margin nearly straight. 



Longest diameter, § of an inch ; height, \ an inch. 



Locality. Cor. Crag, Sutton. 



Red Crag, Sutton, Walton Naze. Recent, Britain and Mediterranean. 



In the sandy portion of the Coralline Crag at Sutton, a locality that has yielded so 

 many of the smaller and more fragile species of Mollusca, numerous small or young 

 individuals of this species may be obtained. My largest specimen was found in the 

 Red Crag at "Walton Naze, and measures an inch in its transverse or largest diameter 

 but it is an old and somewhat mutilated individual. 



When my Catalogue was compiled this was considered to be a distinct species, in 

 consequence of a difference in the size of the ligamental area, as in the Crag shell it is 

 smaller than in the generality of recent specimens, the resemblance was, however, so 

 great in all other respects, that the name of lactanea was given from its near 

 relationship. I have since seen specimens of the recent shell in which this distinction 

 is lost, and have therefore now united it with the long-known recent species. My 

 specimens from the Crag are very regular in form, and I have not met with any 

 fossils resembling the distorted varieties which have been erected into species by 

 Payraudeau under the names of A. Quoyii and A. Gaimardii, the greatest variation 

 being slight differences in proportional dimensions, some occasionally being rather 

 more transverse than others. 



Arca nodulosa, Miiller, given as an inhabitant of the Seas of Norway, by Dr. Loven, 

 corresponding probably with the Calabrian fossil A. aspera, Phil., appears to differ 

 from our shell in being larger and broader on the posterior half, with a more deeply 



