loyS puKssiDKNS 



bent downwards towards the posterior margin so that the 

 vertex of the angle is on the posterior ridge, the upper part 

 of the rear curve is the most prominent part of the beak 

 sculpture and continues down on the posterior ridge for a 

 considerable distance from the beaks. Dorsal slope high, tri- 

 angular. Hinge with a long, compressed cardinal tooth and 

 a long, low lateral in each valve. The cardinal tooth of the 

 right valve and the lateral of the left valve, may have a weak, 

 lamelliform auxiliary tooth above them. Nacre bluish-white, 

 under the beaks salmon-colored. 



To this group belong: P. moellendorjfi n. sp., from Pala- 

 wan and P. insiilaris Drouet from Palawan and Borneo." 

 (Haas). 



Type, Pressidcns mocJicndorjfi Haas. 



PrESSIDIvNS MOKLLENDORPFI Haas. 



"Shell oval, thin, finely and evenly striate. Beaks low, with 

 the sculpture given for the genus, almost wholly eroded in 

 mature specimens, situated at 24/100 of the total length. Up- 

 per anterior margin straight, slightly sloping, with a distinct 

 angle where it passes into the semicircular anterior end, which 

 curves gradually into the horizontal ventral margin ; posterior 

 end obliquely angled ; posterior margin oblique, postero-dorsal 

 angle not strong; dorsal margin almost horizontal, which is 

 nearly as high as the beaks. Posterior slope high ; posterior 

 ridge low ; ligament long, thin. Hinge weak, one lamellifomi 

 cardinal tooth and a slightly curved lateral in each valve ; in 

 front of the cardinal of the right valve there may be a weak, 

 lamelliform auxiliary tooth and above the lateral of the left 

 valve there are noticable indications of another tooth. Angle 

 of the cardinal teeth 25'', of the lateral teeth 0°. Muscular 

 impressions faint. Nacre bluish-white, under the beaks sal- 

 mon-colored. Epidermis chestnut-brown, in young shells light 

 yellowish-brown and also on the worn beaks. 



Length 63, height 38, diam. 20 mm." (Haas). 



Type locality, Paragua. Palawan. 

 Pressidens moellendorffi Haas, Nachr. Deutsch. Mai. Ges., 



1910. p. 103: Conch. Cab., Unio, 1912. pi. 2t^, figs. 3-5. 



