OF SOUTHEEN INDIA. 377 



coi-rected figure of Forbes' original on our plate xxiii, fig. 12. Mytilus cypr'is I 

 believe to be only a young specimen of Modiola typica, Forbes. 



Locality. — Odium, in yellowish brown earthy limestone ; not common. 



Formation. — Ootatoor group. 



MODIOLA, Lamarck, 1799, (see p. 370). 

 1. Modiola typica, Forbes, PL XXIII, Figs. 12-15. 



1846. Mytihis (Modiolus) iypicus et ei/pris, Forbes, Ti'ans. Geol. Soc, Lond., vii, p. 152, pi. 14, fig. 4, and 



pi. xvi, fig. 7. 

 1850. 31. typitus et Lithodomus cypris, d'Orbigny, Prod. II, p. 247. 

 1866. Modiola typica, F., Zittel, Denksch. Akad., Wien, xxv, pt. ii, p. 78, pi. xi, fig. 5. 



BIocl. testa ctineato-ohlonga, paulo arcuata, modice tiimida, antice ohtusata, 

 postice plus mimisve dilatata et ad marginem oblique sub4runcata, ad terminationem 

 postero-inferiorem sub-rotundata ; umbonibus snb-anticis, latis, incurvis, contiguis ; 

 margine dorsali postico convexo, ventrali medio leviter insinuato ; valvis regione 

 ante-mediana ah mnbonibus ad marginem venti^alem decurrente dep)ressa, costulis et 

 striis incrementi concentricis, in parte p)Osteriore multo crassioribus, in convexitate 

 maxima miiltij^licatis, et ante medium maximce elevationis fasciculo obliqno striarum 

 radiantium subtilium decnssatis ornatis. 



There is a good deal of variation to be observed in the Indian specimens as 

 regards the convexity of their valves. Some are more inflated and less high, others 

 less inflated, and in these specimens the posterior half of the dorsal margin is 

 always more extended, forming an elevated compressed crest. The general form 

 closely approaches that of many fossil and recent species (like Ilodiola PJiillipiinarum, 

 Hani.}, but the concentric ribs and stride are much stronger, particularly on the 

 posterior part, and along the ridge of greatest convexity they are much sub-divided. 

 One of the most important distinctive characters consists in a bundle of thin radiat- 

 ing striae, situated on the anterior declivity of the greatest median convexity of the 

 valves, as already pointed out by Forbes and Zittel. The same character is also 

 to be seen in the European fossil from the Alpine Gosau formation. The fulcra 

 which support the ligament extend over a little more than half the length of the 

 shell and are considerably thickened ; the hinge itself is very thin and toothless, 

 as usually in recent Ilodiolce. 



Forbes' Ilytiliis cypris, which d'Orbigny and subsequent authors have 

 referred to the genus Lithodomus, appears to me nothing else than a young specimen 

 of Mod. typica. I have examined Forbes' original specimen, and after exposing it 

 from the adherent rock, I found that the posterior end is much broader than shown 

 in Forbes' figure; I have, therefore, given another representation of this type. 

 A few radiating striae are distinctly ti^aceable about the middle of the valves. 



Localities. — Anapaudy, Koloture, Alundanapooram, Serdamungalum, &c., 

 mostly in a brownish more or less conglomeratic or earthy rock. The species is 

 also common throughout the Alpine Gosau deposits, the fossils from which mostly 

 correspond with those of the Turonien. 



Formation. — Trichinopoly group. 



