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Distribution: — Philippines, Strait of Macassar, New Guinea. 



Hinds says regarding eburnea "This shell closely approaches C. solidula, but 

 is distinguished by its somewhat more triangular shape, polished, ivory-like, flattened 

 valves, and the slightly sulcate sculpture." All these characters are however not 

 constant; among the large quantity of material at my disposal, in which both forms 

 occur, there are evenly transitional forms between the polished, almost smooth 

 eburnea, ornamented with only a few slight transverse ribs towards the ventral 

 margin, and the strongly ribbed, thick-valved solidula. The outline varies some- 

 what, the colour is clear-white in almost all the specimens from the Gulf of Siam. 

 Cuming's specimens of eburnea from the Philippines are of a yellowish colour, but 

 otherwise agree entirely with my individuals from the Gulf of Siam. 



Corbula (?) mirabilis n. sp. 



(PI. V, Figs. 35—37). 



The shell is squarish-oblong in form, flat, thin-valved and white. The umbones 

 are situated towards the posterior end. The prodissoconch is clear, smooth and 

 glossy. Anteriorly the upper margin is straight and passes bj' a gentle arch into 

 the front margin, which forms a semi-circle. The ventral margin is straight, and 

 parallel with the upper margin. The posterior margin passes in an almost straight 

 line obliquely down from the umbo; a rugged keel extends right across the posterior 

 part of the shell from the umbo down to the point at which the ventral and the 

 posterior margins meet. The surface is rough and the lines of growth are coarse 

 and irregular. The interior of the valves is somewhat glossy and the roughness 

 of the surface can here be seen owing to the thinness of the valves. In the hinge 

 there is anteriorly a crater-like depression (probably for the reception of a tooth in the 

 left valve). The margins of this depression have, at the back, a small, pointed tooth 

 and at the front a larger tooth which is continued anteriorly into a long lamella 

 immediately under the upper margin of the valve; beside and somewhat in front 

 of the larger tooth mentioned there are, in addition, upon the upper margin, two 

 tooth-like nodules which project beyond the margin and are visible outside of 

 the shell. Behind the circumscribed depression named is a triangular excision al- 

 most immediately under the apex; upon the upper edge of the thickened posterior 

 margin there is a shallow groove in which, no doubt, the ligament is placed; this 

 groove is limited above by a tooth-like process upon the upper margin which, 

 upon the surface of the shell, resembles a small ear. The front muscle-impression 

 is distinctly visible, but the palliai line only partially; the palliai sinus appears to 

 be wanting. 



Long. 11 mm., alt. 55 mm., crass, (test, dextr.) 1 mm. 



North of Koh Kut, 10 fathoms, mud ('/s). 



The above diagnosis is based upon the solitary (probably right) valve obtained, 

 and I refer the specimen, but with great doubt, to the genus Corbula. In spite ol 



