136 CRETACEOUS GASTROPODA 
XXXIT. TRITONIUM, Link, 1807. 
1. TRITONIUM GRAVIDUM, Séoliczka. Pl. XI, Fig. 14. 
Trit. testa ovate elongata, turrita; anfractibus septenis, ad suturas planiusculis, 
et angustatis, supra medium angulatis, infra lente convexis, transversim costulatis, 
spiraliter striatis, costulis atque strus supra medium multo tenworibus ; margine 
suturali posteriori tumescente et obsolete crenulato; infra medium striis spiralibus 
ternis fortioribus atque in costis transversalibus spinulose tuberculatis conspicuis, 
numerosis minoribus striis alternantibus ; varicibus crassis, posterius spinose angulatis, 
in circuitu anfractuum % distantibus ; apertura subrotundata; labro extus moderate 
crasso, intus ad marginem sulcoso; labio lamelliformi, levigato, postice unidentato, 
medio arcuato, antice crenulato; canali brevi, lateraliter curvo; columella ad 
terminationem anteriorem obsolete fissurata. 
Spiral angle 65°; sutural angle 6°. 
Height of last whorl : total of shell (considered as 1:00) ve 0152. 
An ovate shell consisting of about seven volutions, the last of which is very 
nearly of the same height as the spire. Each of the whorls is posteriorly much 
narrower and flattened, angulated a little above the middle and then slightly convex. 
The posterior edge along the suture is somewhat thickened and obsoletely granulated. 
The transverse ribs are from 14 to 16 in number in each volution, but they are very 
variable in strength in the different specimens; on the flattened portion of the 
whorls they always become thinner, although they never seem to disappear totally. 
The anterior portion of each of the upper whorls is ornamented with usually three 
strong spiral strive, which, in crossing the transverse ribs, form small spinulose 
tuberculations. On the last whorl these spiral striz are of course much more 
numerous, and the transverse ribs become towards the anterior extremity only very 
gradually obsolete. The interstices between the stronger strize and all the flattened 
posterior or upper part of the whorls is covered densely with a much finer striation. 
The varices are very distinctly marked, often ornamented with sharpened tubercles, 
and distant from each other two-thirds of the circuit of each whorl. The aperture is 
roundish; the outer lip thickened externally and grooved internally ; the inner lip 
provided posteriorly with a prolonged tooth, in the middle smooth and anteriorly 
partially crenulated; it is rather thin, lamellar, as is usually the case in typical 
Tritonium, not so enormously thickened as in Stmplum. The canal is short and 
slightly bent to one side and a little upwards. The anterior margin of the inner lip 
being somewhat raised above the surface a slight fissure is formed on the columella. 
Our Indian fossil recalls, as regards the general character or ornamentation, the 
Tritonium Urgonense, Pict. et Camp. (Mater. p. 1. Pal. Suisse, dme. ser. p. 662, Pl. 96, 
Fig. 3), which, although determined from a much smaller and imperfect specimen, 
differs evidently by the coarser and less numerous transverse ribs, and by having 
four stronger spiral strize on each of the upper whorls. It belongs, however, most 
probably to the same group of the Trrroyizpx. 
Locality.—From a light coloured sandstone 8. of Arrialoor; rare. 
Formation.—Arrialoor group. 
