OP SOUTHEEN INDIA. 377 



corrected figure of Forbes' original on our plate xxiii, fig. 12. Mytilus cypris I 

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



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



Formation. — Ootatoor group. 



MODIOLA, Lamarchn^^, (see p. 370). 

 1. MoDiOLA TYPiCA, Forhes, PL XXIII, Pigs. 12-15, 



1846. Mytilus (Modiolus) typicus et cypris, Forbes, Trans. Geol. Soc, Lond., vii, p. 152, pi. 14, fig. 4, and 



pi. xvi, fig. 7. 

 1850. M. typicus et Lithodomus cypris, d'Orbigny, Prod. II, p. 247. 

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



Mod. testa cuneato-ohlonga^ paulo arcuata, modice tumida^ antics ohtusata^ 

 postice plus minusve dilatata et ad marginem oblique suh-truncata, ad terminationem 

 posterO'inferiorem sub-rotundata ; umhonihus sub-anticis, latis, incurms, contiguis ; 

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

 ante-mediana ab umbonibus ad marginem ventralem decurrente depressa, costtilis et 

 striis incrementi concentricis, in parte posteriore multo crassioribus, in convexitate 

 maxima multiplicatis^ et ante medium maximce elevationis fasciculo obliquo striarum 

 radiantium subtilium decussatis 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 Modiola Fhillipinarum^ 

 Hani.), but the concentric ribs and stri^ 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 Ali)ine 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 ModiolcB. 



Porbes' Mytilus 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 Porbes' original specimen, and after exposing it 

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

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

 A few radiating strise are distinctly traceable about the middle of the valves. 



Localities.— Andi^ydiudLj, 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. 



