FISHERY RESOURCES OP THE PHILIPPINE ISLANDS. 



297 



relatively poor showing of the Capiz shells probably is due to the fact 

 that they were old and very dry; they also were somewhat smaller than 

 those from Cavite. 



Table showing the strength of loindoio-shell compared with plate glass. 



Material tested. 



Aver- 

 age 

 thick- 



Aver- 

 age 



weight 

 per 



square 

 cm. 



Number- of falls of a steel ball weighing 

 3.55 grams, necessary to produce failure on 

 samples 2.54 cm. wide and supported at 

 both ends 5 cm. apart. 



Number of 

 blows neces- 

 sary to produce 

 failure with 1 

 kg. weight 

 with a rounded 

 striking end 

 falling 1 cm. 

 high on speci- 

 men 7 by 7 cm. 

 and supported 

 at both ends 6 

 cm. apart. 



Height of fall. 



•50 cm. 



100 cm. 



150 cm. 



Capiz shells 



Cavite shells 



mm. 

 0.8 

 1.1 

 2 

 3 



gms. 

 0.162 

 0.227 



50, not broken 



do 



do- 



6 to 61 



50, not broken 





6 to 73. 

 390 to 1,600. 

 1. 

 2. 



50, not broken 



Glass 





do 



. -do 













GENEEAL ANATOMY OF THE WINDOW-SHELL."' See Plate VIII (a-1). 



These shells when alive are more or less transparent and in younger 

 specimens the functions of the animal may readily be observed through 

 them. Old specimens are thickened and opaque. 



The, largest and most striking object that attracts attention upon opening a 

 window-shell is the mantle, or pallial lobe (Plate VIII, fig. a), which lines the 

 interior of the shell, the margin of which has numerous, fine, finger-like projections 

 forming the pallial fringe (fig. b) ; the mantle usually is much pigmented. When 

 the left valve is removed and the left pallial lobe cut away, the 4 scimitar- 

 shaped gills or branchiae are exposed ( fig. c ) . Near the center of the shell is 

 the round, hard adductor muscle (fig. d) which has been cut in order to open 

 the shell. Directly above the muscle, surrounding the stomach, is the large, 

 yellowish -green liver (fig. e) ; directly to the right of this is the large, yellow, 

 genital lobe (fig. f),; originating just above the highest point of the gills is the 

 foot (fig. g), a long tube-like organ extending to or beyond the edge of the mouth 

 and ending in a disk which is usually full of mud. On the opposite side of the 

 shell is seen a structure slightly similar but much smaller and ending in a disk; 

 thjs is the anal funnel ( fig. h ) . The intestine extends up to the stomach. Near 

 the base of the foot, between two, thin, flap-like membranes, the labial palps 

 (fig. i), is found the small, slit-like mouth. Between the lower genital lobe and 

 the muscle will be seen a delicate, thin-walled organ, the heart (figs, j and k), 

 consisting of 2 auricles and 1 ventricle. The aorta, with some of its large 

 branches, is on the top of the liver. To the left and near the muscle are the 

 kidneys, or nephridia (fig. 1) ; dark colored, elongate organs. By dissecting 

 between these and the muscle, a long, curved, cartilage-like rod is exposed. This 

 is the crystalline style; it ia inclosed in a sac, the pyloric caecum. 



" For a detailed and accurate account of the anatomy and histology of Placuma 

 placenta L. we refer the reader to the excellent work of James Hornell, F. L. S., 

 of the Madras Fishery Bureau, in a Report to the Government of Baroda on 

 the Marine Zoology of Okhamandale in Kittrawar, Part I (1909), 43-99, 5 pi. 



