124 CRETACEOUS GASTROPODA 
2. TRITONIDEA REQUIENIANA, D’Orbigny, sp. Pl. XI, Figs. 8 and 9. 
1842. Fusus Requienianus, D’Orbigny, Pal. Franc, Terr. crét. p. 342, Pl. 225, Fig. 3. 
1851. »  Buchi, Miller, Petrefacten der Aachner Kreideform. p. 35, Pl. V, Fig. 15. 
Trit. testa elongata, spira acuta; anfractibus circiter septenis, convexis, superioribus 
cancellatis, ceteris crasse spiraliter striatis transversimque costatis ; costis 10—12 in 
uno circuitu, ad medium maxime elevatis, antice in ultimo anfractu obsoletis, postice 
tenwioribus, usque ad suturam prolongatis ; striis crassis minutissimis alternantibus ; 
ultimo anfractu maximo, gibboso; canali lateraliter atque suprd recurvo; labio 
tenuissimo. 
Spiral angle 55°—65°; sutural angle 8°. 
The shell consists of four—seven convex volutions, the spire, when well preserved, 
being of about the same length as the last of them. Each of the whorls of the spire 
is ornamented by ten—twelve transverse ribs and about five spiral strie. The two 
uppermost (posterior) of these strize are placed somewhat closer to each other and 
are thinner than the following. When the shell-surface is well preserved a very 
fine spiral striation is perceptible between each of the stronger striz. The anterior 
portion of the last volution is striated similarly to the rest of the shell, but the trans- 
verse ribs disappear perfectly on it. All the whorls are posteriorly somewhat more 
contracted than anteriorly; the ribs are slightly curved, reaching from one suture 
to the other, being, however, posteriorly considerably thinner, while the spiral strize 
increase a little in thickness, where they cross the transverse ribs. 
There exists scarcely any difference, that we could record between our specimen, 
represented in figure 9a and D’Orbigny’s figure. The uppermost whorls are in our 
specimen corroded, and on that account only the spire appears to be somewhat 
shorter. There are ten transverse ribs on each volution in D’Orbigny’s specimen, 
while there are twelve in ours; this number appears to change, however, often in 
one and the same specimen. 
It seems very desirable to compare specimens of Fusus Itierianus, D’Orb. 
(loc. cit. Pl. 223, Fig. 2) with those of the present species, for both the figures of 
D’Orbigny are remarkably alike. The only perceptible distinction is, that the whorls 
are posteriorly somewhat less contracted in the former, but the difference does not 
seem to exceed the limits observed in our materials. The fine striation between the 
coarser in / Itierianus cannot be looked upon as a character of specific difference, 
for it depends merely upon the state of preservation. I have placed the Fusus Buchi, 
Miiller, as a synonym of F. Requienianus, although Dr. Miller says that it differs in 
every way from it. Comparing however the description and figure of the former 
the only difference which can be noted is a somewhat larger number of whorls and 
of transverse ribs; in both these points the identity is perfect with our smaller 
specimen represented in Fig. 8, Pl. XI. The real fact appears to be, that the upper- 
most whorls are gradually worn off with the advanced age of the specimen. The 
variation in the number of transverse ribs has already been noted, and that they 
appear a little sharper, is a matter which may reasonably be expected in younger 
specimens. 
