5 1 2 Zoological Society. 



The group proposed for generic distinction consists of several shells 

 remarkable for their elegance of form and sculpture, but which it 

 has been neither easy to associate with others in established genera, 

 nor advisable, in the absence of all knowledge of the animal, to place 

 apart. Accordingly, they have been variously arranged by different 

 authors. Philippi, in his excellent Enumeratio Molluscorum Sicilies 

 (Berol. 1836), whilst uniting some of them with several species of 

 Eulima, Sow., under the head Melania, Lam., has not failed to re- 

 mark their discrepancy as marine shells from the last-named genus, 

 and to point out the probability of their formation into a genus or 

 subgenus, " quando animalia eorum cognita erunt" : the species 

 which belong to Eulima, Sow., being, after Bronn, considered by 

 him to be congeneric with Niso of Risso. The genus Eulima, as 

 proposed by Risso, consisted of the same exceptionable kind of mix- 

 ture ; but being now ably denned by Sowerby, and restricted within 

 its proper limits to the latter of these groups, the type of which is 

 the Turbo politus of some British authors, I am induced to bring for- 

 ward, in relation to the other, some materials obtained twelve or 

 thirteen years ago, which at the time indeed immediately suggested 

 the formation of the genus Parthenia, but which the progress of 

 Conchology, in the more recent establishment of Eulima, seems to 

 have rendered really interesting. 



The genus Turbonilla (rectius Turbinella) of Risso, though perhaps 

 composed in chief of true Parthenia, is not so constituted, even 

 should this supposition prove correct, as to supersede or clash with 

 the reception of Parthenia. Its definition is extremely incomplete 

 and faulty, and it differs no less in its limits than its constitution ; 

 whilst its very author places in his Eulima and in Turritella some 

 undoubted species of Parthenia. The name, moreover, rightly 

 spelled, is long preoccupied by a well-known genus of Lamarck. 



The group, however, constituted as above, appears sufficiently di- 

 stinct from every other. From Melania it is distinguished primarily 

 by being marine instead of fluviatile, and in the shell being destitute 

 of a dark-coloured epidermis. It differs from Rissoa or Cingula, 

 Flem., in the animal, much as Limncea does from Physa, and in the 

 shell, as Turritella does from Littorina ; whilst from Eulima, Sow., 

 the shells are at once distinguished by their rough or sculptured, 

 ribbed, and generally cancellated surface ; and the animal wants the 

 lateral membranes and subulate tentacula of Turritella, from which 

 the shells also differ in the transverse ribs or plaits of the volutions, 

 and in the shape of the aperture and of the opercle, the nucleus of 

 which is also probably eccentric and anterior ; but this, without de- 

 struction of the specimens, I cannot ascertain. 



The name is formed from TrapQevos, a virgin ; the word -rrapQevta, 

 virginity, expressing well, in contrast with Melania, the simple ele- 

 gance and purity so remarkably characteristic of these shells, which 

 are wholly colourless, and of a spotless milk or ivory whiteness. 



Several recent species of this group are found in the Mediterra- 

 nean, and two at least in the British seas. Others appear also to 

 occur subfossil, in the tertiary beds of Sicily and Nice. 



