58 MOLLUSCA FROM THE CRAG. 
determine its specific character, and it was introduced into my Catalogue as belonging 
with doubt to this species. 
In the recent state this shell is thick and strong, but my specimens differ 
materially in that character, and are particularly fragile. This species exhibits a 
very considerable degree of variation in its outward form or proportional dimen- 
sions, as may be observed in the specimens figured, but a similar variability is 
shown in the living shell: the two forms may be considered as belonging to one 
species, and there can be little doubt of its identity with the shell now common in our 
own seas. My specimens were all found at one locality in association with a bed of 
Myt. edulis. British Conchologists give it vertical range from low water mark to 
sixty fathoms. 
I have introduced as a synonym JM. grandis Phil., believing it not to differ 
specifically from the British shell: some fossil specimens from Sicily (for which I am 
much indebted to Madame Power) in my cabinet, presumed to be the same as 
Philippi’s species, have no character whereby they can be justly separated from the 
shell found upon the coast of Massachusetts. The size of the Mediterranean fossil is 
not sufficient for specific distinction, as a specimen of modiolus, measuring seven 
inches, is recorded by Captain Brown to have been obtained by a fisherman near the 
Bell Rock, on the coast of Forfarshire. 
2. Moproxa Barpata, Linnaeus. Tab. VIII, fig. 2. 
Myritus BARBaATUs. Linn. Syst. Nat., ed. 12, p. 1156, see. Ford. and Hani. 
— — Poli. Test. Sicil., vol. ii, p. 210, pl. 32, figs. 6, 7, 1795. 
Mopiota BARBATA. Lam. Hist. des An. Sans. Vert., t. vi, p. 114, 1818. 
_ — Phil. En. Moll. Sic., vol. i, p. 70, and vol. ii, p. 50. 
— _ Forbes. Report. Agean Invert., p. 180, 1843. 
= — Forb. and Hanl. Hist. of Brit. Moll., vol. ii, p. 190, pl. 44, ‘fig. 4. 
— Grppsi1. Leach. Zool. Misc., vol. ii, p. 34, pl. 72, fig. 2, 1815. 
a —  Turt. Brit. Biv., p. 200, 1822. 
— —_— Brown. Brit. Conch. Ilust., pl. 29, fig. 7, 1827. 
Ency. Meth., pl. 218, fig. 6. 
Spec. Char. Testé tenui, ovato-oblongd, extremitate compressiusculd, anticé brevissimd, 
posticé dilatatd, subangulatd ; liners incrementibus ornata. 
Shell thin, of an oblong-ovate form, posterior portion somewhat compressed, dilated 
and sub-angulated, anterior extremity very short, concentrically striated, or lines of 
increase distinct and prominent. 
Locality. Red Crag, Walton Naze. Recent, British and Mediterranean Seas. 
About half a dozen specimens from the Red Crag, at Walton on the Naze, appear 
precisely in form to resemble what the authors of the ‘ Hist. of Brit. Mollusca,’ seem 
to consider as entitled to specific distinction, and presuming they have good data for 
their determination, I have separated this from where it had been previously placed, 
