FAMILY 11. COLUMELLATA. 249 
popular and much-admired genus, and many of them, though small, are of 
great rarity and beauty. 
The shell of Marginella may be described as being polished, ovately- 
oblong, and emarginated at the base, the spire being short and depressed, 
sometimes nearly concealed ; the aperture is oblong, and in some instances 
equals the entire length of the shell; the columella is plaited nearly 
equally, and the outer lip is so thickly rolled back that it forms a solid 
marginal varix. 
Examples. 
Pl. CCLXXVII. Fig. 1. 
MarGiIneLLa Cieryt, Petit, Magasin de Zoologie, 1836, pl. 73. Kiener, 
Iconographie des Coquilles vivantes, pl. 10. f. 3. 
Pl. CCLXXVII. Fig. 2 and 3. 
MARGINELLA SPLENDENS, (Humphrey, MSS.). Nobis, Proceedings Zool. 
Soc., 1842. 
Pl. CCLXXVII. Fig. 4. 
MarGINELLA NUBECULATA, Lamarck, Anim. sans vert., vol. vii. p. 356. 
Encyclopédie Méthodique, pl. 377. f.2.a,b. Martini, Conch., vol. ii. 
pl. 42. f. 422 and 423. 
Cucumis nubeculatus, Martini. 
Pl. CCLXXVII. Fig. 5 and 6. 
MarGINELLA ELEGANS, Kiener, Iconographie des Coquilles vivantes, pl. 8. 
f.35. Martini, Conch., vol. ii. pl. 42. f.424 and 425. Lister, His- 
toria Conchyliorum, pl. 803. f. 11. 
Pannus striatus, Martini. 
shells, when the animal inhabitants of those shells are the same in every respect. What, then, 
may we ask, constitutes a species, if only such forms are species that perpetuate themselves 
without exceeding peculiar and definable limits? Is there a limit in the perpetuation of any 
form that is not endowed with intellect or reason ? 
