MOLLUSCA FROM THE CRAG. 
Or 
bo 
Two fragments were found by myself in the Coralline Crag at Gedgrave, which 
belong undoubtedly to this genus, and as far as can be determined from their muti- 
lated condition, appear to be of the above-named species; they are introduced here 
provisionally until better specimens be procured than what I possess: my specimens 
of the left valve have an obtuse tooth immediately under the beak within the 
ligamental margin, and are beautifully nacreous within. The area for the ligament 
appears somewhat larger than is shown by the recent shell. 
Mytiuvus,* Linnaeus, 1758. 
Myruuus. Rondelet, 1555, sec. Herrm. 
Muscuuus. List. 1687. 
Mirttus. Browne, 1756. 
Perna (sp.). Adans, 1757. 
Id. Schum., 1817. 
CALLITRICHE et CALLITRICODERMA. Polt., 1795. 
Generic Character. Shell equivalve, inequilateral, oblique, elongate, wedge-shaped 
or subtriangular, more or less tumid, sometimes thin and semitransparent, occasionally 
thick and opaque: in the recent state covered with an epidermis: umbones acute, 
terminal; hinge slightly denticulated; surface generally smooth, sometimes striated. 
Ligament linear, internal. Muscular impressions two, unequal, anterior one near the 
umbo, elongate, posterior one suborbicular near the posterior part of the ventral 
margin: palleal impression without a sinus and rather obscure. 
Animal elongate, with the lobes of the mantle partly fringed, disconnected except 
at the posterior, where there is a short anal siphon: adductor muscles very unequal ; 
a cylindrically formed foot furnished with a gland and groove. 
Animals belonging to this genus are inhabitants of salt-water or estuaries, and are 
generally very littoral in their habits; the common Mussel, as is well known, is more 
often found where it is deserted by the retiring tide, but some are inhabitants of the 
sea at a considerable depth. The living species are found in various parts of the 
world, and in the fossil state have been obtained as low in the secondary series as the 
Cornbrash. 
Mytitus Eputis, Linneus. Tab. VIII, fig. 9, a—e. 
MuscuLus supcmrutnus. List. Hist. Conch., lib. iii, fig. A, 200, 1657. 
Mytitus ppunts. Linn. Syst. Nat., ed. 12, p. 1157, No. 253, 1767. 
= — VULGATISstIMUS. Chem. Conch. Cab. viii, p. 169, t. 84, figs. 750, 751, 755. 
a PELLUCIDUS. Penn. Brit. Zool., ed. 4, vol. iv, p. 112, pl. 63, fig. 75. 
— vuteaRts. Da Costa. Brit. Conch., p. 216, pl. 15, fig. 5, (left-hand fig.) 
— tNcurvatus. Penn. Brit. Zool., pl. 64, fig. 74. 
— ELEGANS. Brown. Illust. Conch. Gr. Brit., pl. 29, figs. 14, 15, 1827. 
* Etym. purfdos (deriv. a pds, as vauri\os a vais). 
