THE NAITILUS. 79 



distinguished by size, proportion, color, habits, and relations to sur- 

 rounding objects and circumstances." Like many things which we 

 understand very well, the word is difficult to define. It is almost 

 impossible to say just what differences are required to constitute a 

 species or a variety. Perhaps so far as the study of conchology is 

 concerned this definition will answer : A viollusk xvhich differs from 

 all allied forms by certain distinct constant characters is entitled to 

 specific rank. As a friend remarked to me : " It is not so necessary 

 that the differences between species be great as that they are con- 

 stant." Any character or characters of real value that are always 

 present on a shell ought to entitle it to a name ; while no matter how 

 marked they may be in individuals, if they imperceptibly fade into 

 those belonging to what have been considered to be other species, 

 they are worthless for purposes of classification. The merest novice 

 who has given any attention to the subject, either collecting or 

 examining cabinets of shells, knows something of how individuals of 

 a species vary. Tliis variation is very often produced by the cir- 

 cumstances by which a mollusk is surrounded, — locality, depth and 

 condition of water, different kinds of soil and bottom, height of 

 elevation on mountain sides, climate and the like. Baron von 

 Tieseuhausen states that Helix cingulata, a smooth shell, is found in 

 the valleys of Austria, H. cingulata var. colubrina, a little mottled 

 and sometimes slightly ribbed, about halfway up the mountains, and 

 H. gobanzi, which is only perhaps a strongly ribbed form of 

 cingulata, lives near their summits. Fasciolaria tulipa, when found 

 in quiet muddy bays is a coarse shell with strongly-marked revolving 

 ridges, of a dirty brownish or ash color and scarcely variegated at 

 all ; and is in every way inferior to the much larger, finely developed, 

 smooth and handsomely variegated specimens taken in the open 

 sea. Natica duplicata, from the vicinity of New England, is a coarse 

 shell often flushed with brown or brownish-yellow, while specimens 

 from the open water in the Gulf of Mexico are smooth and polished, 

 livid in color, or even almost white. The same shell, though, when 

 found in brackish water on the Florida coast, is more like the Xew 

 England form, but is never brownish in color that I have seen. 

 Cyrena floridana is a most variable shell even when a number are 

 taken from the same bed ; so much so that Conrad who just named 

 it, subsequently gave to other very different specimens the appellation 

 of C. protexta. In color it ranges from a dark purplish crimson, 

 through purple and pink to white, and individuals may be found of 



