MOLLUSCA. 
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rounded, the umbones more central; it has more the shape of Baudon’s pL III, fig, D, than 
the last species has. 
Diam. 2|, alt. 2, crass. If mm. 
About a dozen specimens from Yarkand. 
30. PisiDiTJM, n. sp. 
This small form is quite distinct from the two preceding; it can he at once distinguished 
by its great flatness, by being more broadly truncate anteriorly, more produced posteriorly, 
by its very flatly appressed umbones and by its polished glabrous surface; it resembles Bau¬ 
don’s pi. ii., fig. E, (P. thermjale, Bup.), and also somewhat “ Eedsch. Moll.,” pi. iii., fig. 33, 
though apparently the latter does not possess the characteristic appressed umbones. 
Biam. 3, alt. 2^, crass mm. 
Only two or three specimens from Yarkand. 
31. PiSIDIUM OBTUSALE, Pfr. 
Agrees fairly with Clessin’s figure of P. obtusale^ loc. cU.^ pi. ii., fig. 22. 
Biam. 4f, alt. 3f, crass. 2f mm. 
About twenty specimens from Pankong Lake. 
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