116 



Genus 10. FUSUS, Lamarck. 



Animal ; disk someivhat square and comparatively small, usually 



furnished tvith a horny ojjercidum acuminated towards the 



head ; head very small, with two tentacles of moderate lengtli 



in which the eyes are placed, sometimes at the base, sometimes 



towards the middle. 



Shell ; ovately or elonyately fusiform, nerves varicose, canalicu- 

 late d at the base, canal sometimes very short ; columella smooth; 

 lip of the aperture yenerally denticidated. 



It is a feature in the canaliferous tribe of mollusks that a much greater 

 variety of character for the formation of genera is presented in the shell 

 than in the animah and the same may be observed in regard to species. 

 The soft parts of Fmus differ in no material degree from those of Murex, 

 Triton, or Pleurotoma, the disk, head, and tentacles having the same general 

 proportions, wliilst the operculum of each is acuminated anteriorly in Hke 

 manner ; and in the present genus, though one species may have a long 

 turriculated slieU, as in the F. longisslmiis, and another an ovate abbreviated 

 shell, like that of F. despectus, there is no particular variation in the animal 

 except in regard to bulk.* 



The genus Fiisus has, on tliis account, been considered of somewhat 

 doubtful importance ; the knovrledge of this similitude in the animal has 

 even elicited a sort of negative argument in favour of its abandonment, 

 that might be apphed with equal force to any group in the series. 

 " Take away the columellar plaits from the greater portion of the Turbinella," 

 says M. Deshayes in the work quoted below, " and you make Fusi of them ; 

 deprive the Tritons of their varices, and they become Fusi ;" it must, how^- 

 ever, be remembered, that the genera of this class, though systematically 

 characterised by the presence or arrangement of the columellar plaits, are 

 farther distinguished, each by a distinct association of peculiarities. It needs 

 no examination of the varices to distinguish a Mwrex from a Triton or 

 Ranella, and still less of the columellar plaits, to discriminate between 

 the soHd tuberculated Turhinellus and the comparatively delicately nodulous 

 Fusns. The tjqjical difference in the shells of Turhinellus and Fusiis, apart 

 from any consideration of the soft parts, must strike every observer ; and it 



* M. Deshayes inclines to think, from observations he has had an oijportunity of making on 

 the li\'ing Fusus, that there is a difference in the position of the eyes corresponding to these 

 divisions. " If the animals of a larger number of species were known," says that acute observer, 

 " it is probable that the situation of the eyes would afford a character for the distinction of two 

 natural groups, for it may be renuirked that in those species whicli have a narrow elongated 

 canal the eyes are at the base of the tentacles, but in the ovate short-canal species they are 

 upon the middle." — Atiim. sans. vert. vol. is. p. 442. 



