Lamarck's Genera of Shells. 57 



5, Monoceros*. 



Shell oval. Aperture longitudinal, terminating below in an ob- 

 lique notch. Columella generally flattened. A conical tooth at 

 the interior base of the right lip. 



The only distinguishing character between the monoceros and 

 purpura, is the projecting, horn-shaped, conical tooth, on the right 

 lip, which is constant in all the species. 



Type. Monoceros imbricatumt . (Buccinum monodon. Gmel.) 



Shell ovate, ventricose, rather rough, ash colour, or grayish 

 red; ribs crowded, transverse, imbricate-squamous ; whorls con- 

 vex ; spire short; lip crenate. Straits of Magellan. PI. v. Fig. 

 191. 5 Species. 



6. Concholepas. 



Shell oval, inflated, semi-spiral ; summit inclined obliquely to- 

 wards the left margin. Aperture ample, longitudinal, oblique, with 

 a slight notch at the lower part. Two teeth at the base of the 

 right lip. Operculum oblong, thin, horny. 



This singular genus, of which only one species is known, was 

 formerly classed with the patellae. Bruguieres, in consequence of 

 the notch at the lower part of the aperture, and from its having an 

 operculum, perceived that it differs materially from the shells of 

 that genus, and placed it with the buccina, but its peculiar cha- 

 racters forbid its being associated with either the one or the other, 

 or, indeed, with any known genus. Lamarck has, therefore, made 

 it a separate genus, and ranged it next to the monoceros, it hav- 

 ing two teeth at the base of the right lip, instead of only one. 



One Species. Concholepas peruvianus%. (Patella lepas. Gmel.) 

 The usual specific characters are omitted, but the author states 

 below, that the shell is of moderate size, the spire incomplete, de- 

 pressed towards the margin, and furrowed longitudinally. The 



* Unicorn, from juovoc, one, and xtfa?, a horn, t Imbricated — disposed inflates, 



lying one over another, like the tiles of a house. Lamarck's second species ; bis 

 type is M, cingulatum, 



X Peruvian, 



