280 The Philippine Journal of Science wis 



Tridacna gigas Lam. Plate XVI. 

 Mem. Soc. H. N. Paris (1799), 86. 



This is only a fragment of an internal cast, but it is sufficient 

 for determination. The elevated reef limestones of the Philip- 

 pines inclose many fragments and some fairly perfect specimens 

 of this extraordinary shell. The piece shown here represents 

 a shell of about 25 centimeters' length, a young individual. 



OSTREID^E 



OSTREA Linnaeus 



Shell irregular, concentrically leaved or with large radial ribs 

 and folds, arched, frequently compressed, margins simple, entire ; 

 hinge line toothless; beak frequently drawn out, straight with 

 a hinge furrow across it on the underside. Six subgenera 

 including Ostrea. Alectryonia in one of these. Both valves with 

 strong ribs, or folds, shell margins undulating or zigzag shaped. 

 From the Trias on. (Zittel.) 



Ostrea sp. Plate X, fig. 7. 



This is a more or less characterless form which may be entirely 

 normal or some freak form. It may or may not be a new 

 species. If a new species were erected for every queer shape 

 found in the genus Ostrea, the number would be legion. 



Locality: Talamban near Panoypoy, Cebu, No. 274. 



Formation: Mio-Pliocene limestone. 



ALECTRYONIA Fischer 



Shell distorted by early adherance to other objects, mono- 

 noyarian, the anterior adductor absent; edentulous, or with 

 obscure schizodont dentition, dimyarian when young, the foot 

 obsolete or absent in the adult; left valve attached to roots or 

 branches by clasping shelly processes; both valves with strong, 

 often divaricate folds and unduluate margins. Trias to Recent. 

 (Zittel) 



Alectryonia folium Linn. Plate X, fig. 5. 

 Liniueus, Syst. Nat. ed. 10 (1758), 699. 



Neither this genus nor species to my knowledge has been 

 reported from the waters of the Philippines. It does not appear 

 in the Hidalgo catalogue. 



Locality : Sea cliff near Puerto Princesa, Palawan, No. 779. 



Formation: Recent. 



