On the different Ages of Trochus niloticus and T. maximus. 97 
this hypothesis supposes a very great antiquity for these species. 
But this antiquity has its parallel in the Helix labyrinthica of 
North America, which is found in the Kocene deposits of the 
Isle of Wight; and there are many circumstances which tend 
to show a high antiquity for the species of terrestrial Mollusca. 
Port-of-Spain, Trinidad, June 4, 1867. 
XIII.—Conchological Gleanings. 
By Dr. KE. von Martens. 
[Continued from vol. xvii. p. 213.] 
V. On the different ages of Trochus niloticus, L., and 
Tr. maximus, Koch. 
Trochus niloticus is one of the commonest shells in our col- 
lections ; nevertheless it seems not to have been fully understood 
as regards its several stages of growth and its differences from 
its nearest ally 77. maximus, Koch, which, indeed, is figured in 
Reeve’s ‘ Conchologia Iconica’ instead of the true niloticus. 
Chemnitz’s ‘ Conchylien-Cabinet,’ the most complete work on 
_conchology of the last century, contains, in its fifth volume, 
published in 1781, four shells, said to be of different species, 
which are to be referred as follows :— 
Figs. 1605 and 1614, the true Tr. niloticus of Linné, full- 
grown. 
Figs. 1606 and 1607, registered by Gmelin as a variety of the 
former, by Lamarck and Philippi (m Kister’s new edition of 
Chemnitz) as a distinct species, 7. marmoratus, Lam.; by Dill- 
wyn, Deshayes, and Anton, on thé contrary, as the’ younger 
age of Tr. niloticus. This latter opinion seems to me to be 
correct. 
. Figs. 1608 and 1609, cited only by Philippi (/oc. cit.) as a 
variety of niloticus, “ which may be perhaps a distinct species,” 
_I think is a young state of 77. maximus. 
Fig. 1611, called by Gmelin 77. spinosus, regarded by Pfeiffer, 
in his index to Chemnitz’s figures, with some doubt, as a young 
marmoratus, and by Philippi as marmoratus, var. 8. I suppose 
it to be a Tr. niloticus still younger than fig. 1606. 
The full-grown Tr. maximus, Koch, was not introduced as a 
distinct species before the year 1844, when it was figured in 
Philippi’s ‘Abbildungen und Beschreibungen neuer Conchy- 
lien; it appears again in the same author’s treatise on the 
genus Trochus, which forms a part of the above-mentioned new 
edition of Chemnitz, in Kiener’s ‘ Iconographie,’ with the name 
Tr. marmoratus, and in Reeve’s ‘Conchologia Iconica’ as an 
Ann. & Mag. N. Hist. Ser. 3. Vol. xx. 7 
