GLANDINA. 47 
from the sculpture, the varices, and the columella, good as they are in themselves, show 
many degrees of variation according to the different species. The sculpture consists 
generally of vertical (longitudinal) plaits, riblets, or striz, crossed by spiral impressed 
furrows. If both are strongly expressed, the sculpture may be termed “ plexa” (braided); 
in some species the spiral furrows are very weak, scarcely discernible under an ordinary 
lens, and in others they seem to be wanting throughout. It is not easy to clearly 
describe these gradations in a few words, and therefore only the extremes are mentioned 
in the adjoining table. The varices are interruptions of growth, marked by an impres- 
sion and by colour, either a dark streak alone or a dark streak preceded by a pale one: 
they are very distinct and numerous in some species, more or less rare and obsolete in 
others; so that it is not at all satisfactory to form two sections in this genus by the 
presence or absence of varices, as Fischer and Crosse have done. 
Many species have been described only from one or a few examples, and not 
figured; they have been admitted and handed down from work to work by subse- 
quent writers, who have themselves described new species, without the possibility 
of comparing the specimens. As it is rather difficult in this genus to determine the 
species from description alone, and many of them present considerable individual 
variations, it is to be feared that several species have been twice or thrice introduced 
as new, and that the actual number of species is not really so large. I have fortunately 
been able to compare the typical specimens of Shuttleworth’s species (kindly lent me 
by Prof. Th. Studer of Berne), some of Pfeiffer’s types (lent me by Dr. H. Dohrn), and 
drawings of others in the British Museum (kindly furnished by Edgar Smith), with the 
material of the Berlin Museum, which includes Albers’s and many of Strebel’s types, 
and with the shells collected by Messrs. Salvin, Godman, and their friends in various 
parts of Mexico and Central America. ‘This has enabled me to trace many well-charac- 
terized species through various localities, and to diminish the number of so-called 
species by reducing some to mere synonyms or subordinate varieties. On the other 
hand, I have been compelled, somewhat against my wish, to name several new species 
on single or few specimens; and to admit species proposed by previous authors, without 
being able to indicate very striking differences. In this genus, as in many others, it 
seems to be very difficult, or rather impossible, to draw a clear line of distinction 
between local variations and nearly allied species. Only one who can observe many 
specimens in various localities, and one who is well acquainted with the minute 
differences, can hope to settle this question. At all events, I have been able by the 
help of my friends to figure many—true or pretended—species which have not hitherto 
been figured, and were therefore scarcely recognizable by the practical conchologist. 
The Mexican and Central-American species of this genus may be arranged as 
follows :— 
A. Pleve: sculpture more distinctly granoso-reticulate; aperture 
large; sizeratherlarge . . . 2. . . . . . ee. imdusiata, vanuremi, 
sowerbyana, coulteri, cuneus, aurata. 
