12 NOETLING : MARINE FOSSILS FROM MIOCENE, UPPER BURMA. 



Remarks. — Although at the first sight the two species of Batissa 

 here desribed are so similar that it seems nearly impossible to dis- 

 tinguish them, a closer examination will at once show the charac- 

 ters by which they differ. There is no difficulty if the hinge is 

 exposed, because the weaker hinge at once distinguishes Batissa 

 petrolei even in fragments, from Batissa crawfurdi with its strong- 

 ly developed teeth ; but if the two valves are united, it is not always 

 easy to say to which species a single shell might belong ; however, 

 the following features will characterize B. petrolei :— 



The shell is much less inflated than that of B. crawfurdi. Owing 

 to beaks being nearer to the median line, and not so much turned 

 forwards, the shell has a more oval shape ; the shell is much 

 thinner than that of B. crawfurdi. 



If the limits of the two species are drawn as above, there is not 

 the slightest difficulty in keeping them separate, even if fragments 

 only are found. This seems to me very important, because, if I 

 rightly conclude, Mr. Theobold's Cytherea promensis, the original of 

 which I could not find up to the present, must be identical with 

 either B. crawfurdi or B. petrolei ; the horizon characterized by 

 these two species would therefore apparently be also represented in 

 the tertiary of Lower Burma. 



VENUS, cf. SCALARIS, Bronn, Plate III, Fig. 4. 



1870. Venus scalaris, Hoernes, Die Foss. Moll. d. Tert. Beck. v. Wien. Abhandl. d. 

 k. k. Geol. Reichs. vol. IV., 1870, page 137, plate XV, fig. loa-c. 



An isolated valve, measuring 9 mm. in height, 9 mm. in length, 

 of sub-orbicular shape, probably belongs to this species ; the external 

 characters cannot be seen well, because the surface is covered with 

 sand which cannot be removed without destroying the shell ; but it 

 appears that it was covered with sharp, horizontal ribs, separated 

 by broad furrows of about double the breadth of the ribs. A small 

 well defined lunula present ; the hinge shows the usual character ; 

 the ventral margin is slightly crenulated inside. 



Locality.-— Very rare at Yenangyat. 



Remarks.— \t is unfortunate that only one specimen of this form 



( 12 ) 



