192 CRETACEOUS GASTROPODA 
the pure marine water has free access, they are generally wanting, while at or 
near the mouths of great rivers, or in brackish swamps and lakes, they are most 
abundant. In the fossil state we have, therefore, to look for them only in deposits 
formed under similar conditions. They are not wanting either in the Vienna, or in 
the Paris and London basins, at Ronca in Venetia, and numerous other places in 
the tertiary epoch (Cerith. Duboisi, Horn.; Cer. margaritacewm, Broce. ; Cer. elegans, 
Brug., and others). 
Among the secondary deposits we find the roramzpivx equally represented 
in cretaceous beds, and they have been traced with certainty also in the Wealden 
deposits. As regards the cretaceous species, I can only refer to my ‘ Revision of 
the Gosau Gastropoda’ (Sitz. Akad. Wien, 1865, Vol. LIT, p. 91, ete.), where I have 
attempted to prove that the largest number of the Czrzrazrp# from those deposits 
belong to the poraurpinm. I have, however, nothing to add to this sub-family from 
South India. 
a. Sub-family—CLRITHIIN A. 
XLVI. CERITHIUM, Adanson, 1757. 
1. Crritatum (FiBuLA?) DETECTUM, Stoliczka. Pl. XV, Fig. 1. 
Cer. testa acute turrita; anfractibus circiter septenis, altis, levigatis, postice 
ad suturam paulo contractis, antice et ad medium subconvexis, varicibus nonnullis 
distantibus atque depressis interdum notatis; ultimo ad basim obtuse ac rotundate 
angulato; apertura ovata, postice acuta, antice canali brevi, contorto atque paulo 
lateraliter curvo termimata. 
Spiral angle 24°; sutural angle 15°. 
Height of last whorl : total of shell (considered as 1:00) 0°34 
Height of penultimate whorl : height of the spire (considered as 1:00) ... 0:20* 
BE Wet 5 5 : its width (considered as 1:00) ae Be 0:68 
In the smooth surface of the shell this species agrees with the jurassic 
Fibule, and its recent representative Cerith. leve, Q. and Gaim., which, as I have 
already remarked, is not a Zelescopiwm, although the columella is nearly quite as 
tortuous as in the typical Zelesc. fuscum. : 
The principal characters which . distinguish our cretaceous species are the 
comparatively great height of the. whorls as to their width and the occasional 
slight varices, which appear on the surface, being preceded by a deep furrow. 
Below the sutures all the whorls are somewhat contracted, the rest bemg slightly 
convex, and the last one obtusely angulated. The aperture is ovate, considerably 
narrowed towards each end, anteriorly terminating with a short canal, bent laterally 
rather than recurved. 
* If not otherwise stated I take these proportions on the back view of the shell, although the results donot very materially 
later if taken on the front view. 
