420 Original Articles. [July, 
But we have seen that one species of Neritina is keeled and tuber- 
culated, while another presents ordinary characters, that the Unio is 
unnaturally thick, and, except one specimen, very much stunted, 
while the most abundant species of Melanopsis is represented both by 
small specimens normal in character, and by large examples unna- 
turally coarse and ribbed, to say nothing of the wonderful Melania. 
How, therefore, can we account for the entombment of species which 
lived under normal conditions in association with specimens of the 
same and other species that evidently lived under circumstances not 
quite suited to them? Bearing in mind that the normal specimens 
belong both to fresh-water and estuarine genera, and that the abnormal 
ones are wholly fresh-water, as well as the fact that all of them could 
exist in brackish water, being either operculated gasteropods or 
bivalves, and not belonging to purely fresh-water genera, it appears 
to me that the only way of accounting for the association is by 
supposing that the deposit was formed in a lagoon, which was 
subject to occasional irruptions of salt water, and into which a river 
flowed. 
This conclusion is very similar to that arrived at by Professor 
Forbes and Captain Spratt respecting the Cos fossils, only that they 
assumed the lagoon to be at first quite fresh, and to have become 
gradually saline, and they did not call in the aid of a river; but 
the occurrence of the Unio and of normal and abnormal specimens of 
Neritina, &c., appears to render the latter device necessary in this 
case. In the lagoon, al] the species could exist for a time, after 
having been carried down by the river, and thus the abnormalities 
described may have been produced. 
APPENDIX. 
I.—Drsorrprions or NEW SPECIES FROM CRETE. 
1. Neritina abnormis, mihi. Figs. 7a to Te. 
Shell broadly ovate, trochiform, ornamented with brownish zig-zag longitudinal 
lines or bands; whorls three, crowned by a broad cord-like keel, and with a 
thinner and sharper ridge in the middle, often corded or crenate, and sometimes 
tuberculated or irregularly spiniferous, separated from the upper keel by the con- 
cave upper portion of the whorl. Mouth in a plane nearly at right angles to 
the axis, more or less semilunate in form; inner lip concave, smooth, with a broad 
callosity covering the base of the shell, and becoming very thick and encroaching 
on the mouth in old specimens. 
2. Neritina Spratti, mihi. Figs. 6a to 6d. 
Shell ovate, smooth, orn: imented with many blackish spots, more or less 
regularly arranged ; whorls three or four, declining above, sometimes compressed 
in the middle, convex at the base. Spire depressed, blunt. Mouth oblique, 
irregularly semilunate in form ; inner lip concave, callous, minutely dentate 
3. Melania? anomala, mihi. Figs. 3a, 3b. 
Shell thick, reversed, turreted, ovate, somewhat obtuse at the apex; whorls 
about seven, slightly convex, transversely and longitudinally ridged; transverse 
ridges coarse and blunt, obsolete on the uppermost whorls, and oradually i increas- 
ing in number, from two on the third whorl to four on the body-whorl ; longitudi- 
nal ridges obsolete on the upper whorls and becoming gradually more apparent on. 
the lower; they are the same distance apart as the transverse ridges, which they 
. 
