MARTESIA. 231 
Famly—PHOLADIDA, Leach. 
Genus—Marvresia, Leach in H. M. D. de Blainville, 1825. 
(‘ Manuel de Malacol.,’ p. 632.) 
Marresta consrricta (Phillips), 1829. Plate XXXVIII, figs. 3—10. 
1829. PuHotas constricta, J. Phillips. Geol. Yorks., p.169 (p. 256, ed. 3), pl. 1, 
tito life 
1850. — = A. d’Orbigny. Prodr. de Pal., vol. ui, p. 117. 
1854. — == J. Morris. Cat. Brit. Foss., ed. 2, p. 221. 
1864, — — F. J. Pictet and G. Campiche. Foss. Terr. Crét. Ste. 
Croix (Matc¢r, Pal. Suisse, ser. 4), 
p. 26. 
1870. — — F. Stoliczka. Paleeont. Indica, Cret. Fauna 8. India, 
p. 23 (? Martesia). 
1900, PHonapipEa constricta, A. J. Jukes-Browne. Cret. Rocks of Britain, 
vol. i, p. 470. 
Description.—Shell small, more or less elongate; anterior part short, convex, 
rounded; posterior part wedge-shaped. Umbones prominent, close together, 
curved inwards and forwards. Ventral margin nearly straight. Posterior margin 
sub-truncate, more or less rounded, somewhat oblique. Postero-dorsal margin 
sloping ventrally. Two narrow furrows, with corresponding internal ribs, extend 
from the umbo to the ventral margin; the anterior furrow is rather broader and 
less oblique than the posterior, but is sometimes short or absent. An internal 
ridge, near the postero-dorsal margin, extends from the umbo to near the posterior 
adductor. Anterior callus shield-shaped. Ventral margin of valves diverging 
posteriorly, jomed by a hypoplax. Metaplax elongated, divided. 
Ornamentation: on the larger part of the shell distinct, regular, concentric 
ribs with minute transverse serrations. In front of the anterior furrow the ribs 
become smaller and closer together; they bend dorsally and unite at an angle 
with similar ribs on the dorsal part of the anterior end of the valve. On the 
postero-dorsal part of the shell the ribs are less regular and less distinct. 
Measurements : 
Q) (2) (3) (4) (5) (6) (7) 
engthe eo VS) 17, 16 18 15 14, HORS ama 
Hero hiGe Sen. nO 8. Ore seat) pts Oy ane ote ow ox 
Thickness Deets Des Oe kO Se SOR eoremaOnS 
(1—3) Speeton, (4—7) Folkestone. 
Affinities—This species is less elongate than M. subcylindrica (VOrbigny).’ 
1 «Pal. Frang. Terr. Crét.,’ vol. iii (1845), p. 306, pl. ceexlix, figs. 5—8. 
