378 CRETACEOUS PELECYPODA 



2. MoDiOLA NiTENS, Forbes, PI. XXXVIII, Fig. 6. 



1846. Mytilus nitens, Forbes, Trans. Geol. Soc, Lond., vii, p. 151, pi. xvi, fig. 8— idem auctonim. 



Mod. testa ovato elongata, tenui ; valvis modice suh-conveods, antice angustate 

 rotundatis; postice compressiusculis, setisim dilatatis et ad marginem sub-rotundatis, 

 depressione obliqua paulo profunda ab umbonibus ad marginem antero-ventralem 

 deciirrente, umbonibus anticis, latiuscuUs, depressis, superficie striis incrementi acufis, 

 confer t is et tennibns tec fa, 



A small species witli a thin shell, elongately ovate, being narrowly rounded 

 in front with almost quite terminal beaks and a shallow rather short depression 

 running from them to the ventral margin ; the posterior part of the shell widens 

 considerably and becomes very flattened towards the rounded margin. The 

 surface shows only fine, sharp concentric striae of growth, but no radiating lines, 

 which are so characteristic for Mod. typica, from which species the present shell 

 also differs by the smaller convexity of its valves. The same difference applies in 

 a comparison of our species with M. Oppeli oi Zittel. Forbes' original figure 

 represents a smaller specimen, but the ventral portion should be a little broader 

 at the anterior end, the species being a Modiola and not a Mijtilus. 



Locality. — Olapaudy, in a yellowish earthy rock ; apparently very rare. 



Formation. — Arrialoor group. 



3. Modiola polygona, d'Orbigny, PI. XXIII, Figs. 10-11. 



1846. Mytilus (Modiolus) pulcher, Forbes, Trans. Geol. See., Lond, vii, p. 153, pi. xvi, fig. 6, non idem 



Pbillips, nee Goldfuss. 



1847. Mytilus pohjgonus, d'Orbigny, Voy. Astrolabe Pal., pi. v, figs. 41-42 ; — idem auctorum (non jiulcherri- 



nus, errore typico, in d'Orbigny's Prodi'ome). 



Mod, testa sub-tetragona, regione ah umbonibus ad tei'minationem postero-inferi- 

 orem diagonaliter extensa rotundate carinata, antice sub-rotundata, postice oblique 

 truncata, margine dorsali brevi, recto, ventrali fere recto, vix insinuato, umbonibus 

 sub-terminalibus, anticis, Icevibus, valde incurvis, approximatis ; sujjerfcie striis 

 incrementi temiibus et alteris radiantibus subtilissimis et confertissimis, vix conspicuis, 

 ornata. 



A very marked, obliquely sub-quadrangular and moderately tumid form, 

 each valve being diagonally provided with a rounded ridge, which more or less 

 projects posteriorly and thus slightly alters the form of the shell. At the margins 

 the valves are peculiarly attenuated, forming sharp edges. Besides the striae of 

 growth which are sharp and very fine, there is almost on the entire surface a very 

 minute radiating striation perceptible under a lens. 



Locality. — Pondicherry, in a light bluish grey sandstone; apparently not 

 common. 



Formation. — Valudayoor group (?). 



