38 FAUNA OF BALUCHISTAN. 



irregular rounded radiating ribs, which are only very faintly expressed. 

 The right valve is flat, the beak very short and pointed. Surface smooth, except 

 some very strong irrogular strise of growth which make the surface appear some- 

 what rugose. 



Locality and atratigropMcal position. — Mazdr Drik, horizon 8. 



Btmurks. — By their general shape and compressed valves, exhibiting a very 

 pointed umbo, the Baluchistdn specimens are proved to belong to this wall known 

 species. According to Coquand this form characterises theetage Santonien, but it 

 appears from his list of places where it has been found, that it probably ascends to 

 a higher horizon. 



OsTREA (Alectrtonia) pectinata, Lamarck. PI. IX. fig. 2, 3-3a. 



(Synonymy in Coquand, Mouographie du genre Ostrea, p. 76.) 



None of the specimens which have come under examination show a perfectly 

 preserved shell, but still it may be seen that they belong to a narrow form which 

 was moderately curved backwards, and which must have attained a considerable size 

 and thickness. The ornamentation of the valves consists in very strong rounded 

 ribs, which from being simple in the middle bifurcate at the sides. The posterior 

 margin is very thick and nearly perpendicular, the anterior margin somewhat 

 sloping. 



Locality and, stratigraphical position. — Mazdr Drik, horizon 8. 



Bemarks. — This species is one of the most characteristic fossils of the upper 

 cretaceous strata, and, as far as known, chiefly characterises the etage Santo- 

 nien. In Southern India it has been found in the Ariyaliir group. 



Ostrea (Alectryqnia) ungulata, Schlotheim sp. PL IX. fig. 4-4b, 5. 



(Synonymy in Coqaand. Monographie du genre Ostrea, p. 58.) 



The shell is sigmoid, very narrow, and somewhat compressed at both ends. It 

 attains its greatest thickness at the anterior margin, and the surface of both valves 

 slopes froni there posteriorly. The anterior side is therefore high and thick, the 

 posterior side low and sharpened. Both valves show the same ornamentation, which 

 consists of short single ribs, lining the anterior and posterior margin, but not extend- 

 ing towards the central part of the shell, which remains smooth : this smooth medial 

 space is one of the chief features of the species. On the anterior margin the inter- 

 stices between two ribs take the form of long sharp teeth which deeply notch the 

 ribs of the opposite valve. On the posterior margin the ribs are somewhat longer, 

 particularly on the expanded area just below the beaks, where they are slightly 

 curved, thin and sharp. 



Locnlity and stratigraphical position. — Mazar Drik, horizon 8. 



.ft«='mflrA« — Stoliczka aptly remarks that this species characterises the upper 

 cretaceous beds of almost all parts of the world. We may now add Baluchistan 

 to the countries which Stoliczka enumerates. 



