250 MOLLUSCA FROM THE CRAG. 
MesopEsMA JaurEsit. De Joannis. Mag. de Zool. Moll., pl. 54, 1834. 
— = Gould. Invert. Massach., pl. 58, fig. 38, 1841. 
— pEauRATA. Forb. and Hanl. Hist. Brit. Moll., vol. i, p. 346, 1848. 
ERYCINA DENTICULATA. Cuvier. (Grifiths.) An. Kingd., t. 22, fig. 2. 
PAPHIA DEAURATA. Gray. List Brit. Moll.; p. 157, 1851. 
Spec. Char. Testa transversd, oblongo-ovatd, inequilaterali, crassa ; transverse striata 
vel subimbricatd ; anticé longiore et rotundatd ; postice truncata ;. cardine bidentato ; denti- 
bus lateralibus magnis, striatis. 
Shell transverse, ovately oblong, inequilateral, thick and strong, transversely or 
concentrically striated; anterior side the longer, and rounded; posterior truncated ; 
lateral teeth large, and perpendicularly striated. 
Length, \} inch. Height, 2 inch. 
Locality. Red Crag, Sutton, Walton Naze. 
Recent, North-east Coast of America, Newfoundland. 
The specimen figured was found at Walton-on-the-Naze by John Brown, Esq., of 
Stanway. There is another in my own cabinet, from the Red Crag at Sutton, but not 
in quite so good a state of preservation. It may be thus more fully described: The 
anterior side is much produced, the base line of the shell ascendmg towards the 
extremity, where it is roundedly pointed, while the siphonal side is very short, and 
obtusely biangulated ; the surface is covered with irregularly elevated lines of growth 
or ridges; corresponding with the figure and description given by Turton, who says 
it somewhat resembles in outline J/. dea/bata, but differs in being thieker, and 
also in the teeth, though he does not tell us what these latter are like in either 
species. 
The recent shell is placed by some authors in the genus J/esodesma. A small 
A-formed tooth is present in this left-hand specimen, placed immediately before a 
large ligamental area, as in Jactra, with elongated lateral teeth, which are striated. 
Lurraria,* Lamk. 1799, 
Macrra (sp.) Linn. 
PsamMopnita. Leach, MS. 1819. Fide Brown. 
Lurrtcota (sp.) De Blainv. 1824. 
Generic Character. Shell transversely ovate or oblong, inequilateral, and gaping 
at the lateral extremities ; externally smooth, or slightly striated transversely. Hinge 
with a prominent triangular or diverging tooth in the right valve, with a corresponding 
pit for its reception in the left. Ligament internal, placed in a large spoon-shaped 
depression in each valve. Impression by the mantle deeply sinuated. 
* Etym. Luéra? a luto, to daub, probably from its mud-like exterior. 
