182 EOCENE MOLLUSCA. 
In the general form of the shell, the condition of the apex and of the outer lip, 
the columellar plaits, and the deep anterior notch, this M/itra so much resembles 
M. labratula, that it might almost be regarded as merely a variety of that species in 
which the longitudinal ribs and transverse lines found in the young state have been 
continued on the mature shell. I have not, however, met with any smooth specimen 
of the present species, and mature individuals of J. /abratu/a are, apparently, always 
smooth, with the exception of a few obscure transverse lines near the suture, or at the 
base. This want of intermediate forms, therefore, confirms the title of JZ. scabra to 
specific distinction. 
Size.—Axis, 11-12ths of an inch; diameter, 5-12ths of an inch. 
Locality—The species appears to be confined to the Barton beds. I have not 
met with it elsewhere. 
No. 119. Mirra LaBRATULA. Lamarck. Tab. XXIV, fig. 3 a, 6. 
Mirra LaBRraTuLa, Lamk. 1803. Ann. du Mus., vol. ui, p. 58, No. 5, t. 3, fig. 6. 
— LABRATELLA, J6. 1816. Tab. Encycl. et Method., t. 392, fig. 3a, 8. 
— .LaBratuLa, J6. 1822. Hist. Nat., vol. vii, p. 325, No. 5. 
— — Defr. 1824. Dict. des Sci. Nat., vol. xxxi, p. 491. 
— — Desh. 1830. Encye. Méthod. (vers.), vol. ii, p. 465, No. 42. 
= — Ib. 1824—37. Deser. des Coq. Foss. &c., vol. ii, p. 672, t. 88, figs. 
9, 10, 18 and 19. 
— — Meller. 1843. Mem. sur les Sables tert. inf., &c., de Paris, p. 17. 
-_- — Roissy. - Buff. Moll., vol. v, p. 443. 
— monoponta, Sow. (non Lamk.) 1850. Dix. Geol., &c., Suss., p. 106, t. 7, figs. 20, 21. 
— taBratuLa, D’Orb. 1850. Prod. de Paléont., vol. ii, p. 354, No. 296. 
M. testa ovato-acutd, levi, aliquando in juventd costulis et striis transversis decussatd, 
ad basin profunde emarginatd : spird conicd, apice obtuso: apertura elongata, angustd ; 
labro incrassato, sub-marginato, intus unidentato ; columella quadriplicata. 
Shell ovately oblong, slightly ventricose, smooth; sometimes in French specimens 
the early volutions present obscure undulating ribs, decussated by irregular, transverse, 
fine, raised lines, which altogether disappear on the last volution, or are reduced to a 
few faint lines, nearly obsolete, at the base, or round the sutural margin: the spire is 
conical with an apex formed, like that of J/. scadra, of two roundish embryonal whorls, 
and, as in that species, the base is deeply notched, and bent backwards. The aperture 
is of a long, ovate shape, and rather narrow; the outer lip thickened, slightly bent 
outwards, so as to form a narrow, raised border along the outer margin, and furnished, 
generally, with a blunt, tooth-like callus on the inner edge, near the posterior extremity ; 
the columella presents four prominent, almost transverse folds, the posterior three of 
which are nearly equal, and are larger than the one in front. ® 
