PIIOLADOMYA DEPACTA. 41 



Three casts. Dimensions of largest (figs. 8 a, h) : length, 35 mm.: height 

 32 1 , mm.; thickness. 28 nun. ; — of second cast (fig. 8 c) : length, 27| mm.; 

 height, 25 mm.; thickness, 23 mm. 



The largest specimen is unsyinmetrical, owing partly to distortion through 

 pressure, but perhaps in part to original inequality of the valves. In the 

 other two examples, the beaks, which in this have been forced into contact, 

 are two millimeters asunder. The flattened anterior face answers well to 

 Agassiz's diagnosis of the genus, and to figures of several of his species. 

 The deep dorsal depression between the umbones is analogous to the cor- 

 responding part in several recognized species of Ceromya. The hinge was 

 undoubtedly edentulous. The three casts bear crowded concentric striae, too 

 indistinct to be well figured, but very perceptible. These and the absence 

 of any traces of muscular and pallial impressions indicate that the test was 

 very thin. Stoliczka identifies a single species of Ceromya in the Cretaceous 

 of Southern India. 



Conrad's description and figures of Opis orientalis (Official Report, p. 231, 

 App., PI. ii, figs. 10 a, b) may possibly refer to this species, but are vague and 

 unsatisfactory. Coll. Thomson. 



Locality and Position. — Probably from Beirut district, and from the 

 Turonian. 



Pholadomya depacta, sp. nov. 



Plate VI. figs. 6 a. b. 



Nuclei's ovato-oblongus, cequivalvis, perincequilcderalis, costulis radianMbus anyustis 

 circifcr quindecim notctius : pars antica brevissima, obtusa, postica dilatata, com- 

 pressiicseula, oblique truncata ac mediocriter Mans : umbones in/Mi pcene terminates, 

 depressi, inter se atiingentes: margo veniralis arcuatus, dorsalis oblique retrocur- 

 vatus : lunula absens ; area cardinalis anyuste lanceolata. 



Cast ovate-oblong, equivalve, extremely inequilateral, bearing about 

 fifteen narrow ribs radiating from the beaks: anterior portion very short 

 and obtuse; hinder part widened, somewhat compressed, obliquely truncate 

 and at the truncated edge moderately gaping: the inflated umbones almost 

 terminal, depressed, contiguous : ventral margin arcuate ; dorsal margin slan- 

 tingly curved backward: lunule wanting : posterior area narrowly lanceolate. 



Single specimen, a cast. Length. 48| mm.; height, 44 mm.; thickness, 

 26 mm. 



