10 NOETLING: MARINE FOSSILS FROM MIOCENE, UPPER BURMA. 



of growth, which are rather closely set on the anterior side, thereby 

 creating a kind of pseudo-ribbing. 



Dimensions, 



Height. Length. Thickness. 

 Largest specimen 1 . 49mm. 51 (?) mm, 35 mm. 



Average sized specimen . 38 „ 40 „ 26 „ 



Locality.— Partly in, but chiefly just above, the zone of Hippo- 

 therium antelopinum, very common, but only locally ; for instance 

 north-east of Minlindoung any number of specimens might be col- 

 lected. 



Remarks, — The character of the hinge, as well as the general 

 shape and the strongly developed ligament, fix the generic position 

 of this species ; the only doubt which existed was with regard to 

 the lateral teeth, of which there are two only in the left and none in 

 the right valve ; considering, however, the great similarity of this 

 species with the recent Batissa tene&rosa, I think this difference not 

 sufficient to justify a new genus. 



Batissa crawfurdi differs from Batissa petrolei'm the general shape 

 by being (1) more inflated, (2) the beaks being turned more towards 

 the anterior side ; although very marked when numerous specimens 

 are under examination, it is not always easy to say of a half-grown 

 specimen to which species it belongs. In this regard the hinge 

 affords the best distinguishing character, it being always very 

 strongly developed in Batissa crawfurdi, while that of Batissa 

 petrolei is much less powerfully constructed. Besides this charac- 

 ter Batissa crawfurdi can easily be recognised by its thick shell, 

 particularly in the umbonal part. 



Batissa crawfurdi has quite a history, so to speak ; although it is 

 known since the year 1829, when it first was mentioned by Crawfurd,* 

 who, to judge from his description, visited the locality which has 

 been marked on my geological map of the Yenangyoung oil-field 



1 The posterior side of the above specimen being broken off, the exact length cannot 

 be given, but to judge from other specimens its length cannot have been less than 

 51 mm. 



8 Crawfurd's Jaurnal of an Embassy to the Court of Ava, London, 1629, 

 page 329. 



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