180 EOCENE MOLLUSCA. 
Genus 24th. Mrrra.* Lamarck. 1801. 
Mirra, Turris, Montf., 1810. 
CyzinpRa, Impricaria, Schum., 1817. 
Trara, Mirreona, Con@iix, Mitretia, Swains., 1840. 
VuLprcuta, Gray, 1840. 
Gen. Char.—Shell fusiform, smooth, longitudinally ribbed or cancellated; spire 
elevated, pointed: aperture longitudinal, narrow, notched at the base, and without a 
canal, or at most with a very short one; outer lip sometimes thickened, generally 
sharp-edged, internally smooth or crenulate; columella plaited, folds regular, nearly 
transverse, the anterior one the smallest. 
The Mitres are distinguished from the Volutes, with which they had been associated 
until they were separated by Lamarck, by their more elongated, less ventricose form, 
and by the character of the columellar plaits, which are more transverse and regular, 
with the smaller one in front, a disposition the reverse of that which characterises the 
Volutes. 
The animal has a small, narrow head, with short, pointed tentacles, on the external 
sides or bases of which the eyes are placed; but some species from the Mediterranean, 
according to M. Deshayes, bear pedicels much shorter than the tentacles, united 
to them, and terminated by the ocular points. The foot is narrow, truncate in front, 
pointed behind; and the anterior margin of the mantle is produced into a short, 
cylindrical canal. But that which chiefly distinguishes the animal of J/itra, is the great 
length of the proboscis, which, in some species, considerably exceeds that of the shell. 
The Mitres, as defined by Lamarck, have been subdivided into several genera, 
dependent chiefly on conchological distinctions. In some of these divisions the 
animals, according to observations recently made by Dr. Gray, exhibit modifications 
of the lingual teeth closely resembling those characteristic of other genera; and that 
eminent naturalist, therefore, regards the J/tre as forming a family distinct from the 
Volutide, with which they have usually been associated. The small, narrow foot, and 
elongated proboscis lead, apparently, to the same conclusion. 
The living J//tre are very numerous; upwards of 350 species being known ; 
of these one is from the coast of Greenland, and some few small species are found in 
the Mediterranean. With these exceptions, the J/tre are confined to tropical or sub- 
tropical seas, where they are found, according to Messrs. Adams, chiefly on the shores 
of islands, but few species inhabiting continental shores. They appear to be deep-sea 
molluscs, most of the species ranging in depth from 15 to 80 fathoms, although some 
few are littoral. 
* Etym. Merpa, a turban or covering for the head, worn by the Persians and other Asiatics. 
