20 NASSA. 



Marrat, is the lyrate Ibrm ; ^V. tricarinata, Lam., is the carinated 

 form; ^V. .sc(///)^n!, Marrat, is another; N. sidroides^ l^eviW^ N. 

 trinodosa, Smith, and N. corticata, A. Ad. Another variety 

 occurs, showing a ch)se affinity with the N. murirata^ Qiioy «'ind 

 Gaim., and the shell figured in Reeve's Concliologia Iconica as 

 the N. vib«>x, Say, is a spiny form. Some of the shells from 

 Ceylon are very closely connected with varieties of the N. 

 Gruneri. Dunker, and others with smoother ribs to the N. Jack- 

 aoniana, Quoy and Gaim. 



" We may name these shells and describe them as distinct, but 

 they will not be so after we h'ave finished; on the contrary, we 

 may adojit another plan and name them varieties, but the same 

 objection continues; the variety we have named as coming from 

 any locality will be found to dilf'er from the shells brought up 

 from the same ground l)y the next haul of the dredge. It is a 

 very disagreeable task to Ite compelled to state tliat the starting- 

 point of the systematist, upon which the whole fabric is Imilt 

 up, is wrong, and the whole of tlie deductions drawn from this 

 source are erroneous; nevertheless I am compelled to utter tliat 

 which I believe to be strictly and un(piestionably true. I can- 

 not exi)ect that conchologists who are totally unacquainted with 

 the materials upon which I have based ni}^ deductions, will 

 coincide with m^^ views. If they had obtained a knowledge of 

 the whole of the figured or described species of Nassa, they 

 coidd not by this plan follow the intricate passages revealed by 

 the study of variation. It is not b^"^ an intimate knowledge of 

 the described species that these facts are elicited, but it depends 

 upon a knowledge of the innumerable intermediate forms which 

 diverge from them in every direction as to how these deductions 

 are to be drawn. 



" In a long series of forms, commencing with shells represent- 

 ing the largest specimens in the genus, these can lie traced with 

 unerring certainty into others, forming the smallest examples 

 known to exist; again, the broadest varieties can just as easily 

 be connected with others that are the narrowest examples in the 

 group; and every grade of difference throughout tlie long lines 

 of progressive variation is distinctly seen. In tiie case of the 

 shells having smooth forms, such as N. (/l('n!<, Linn., the varieties 

 may not be all smooth specimens, but they may \ary into costate 



