26 NEW YORK STATE MUSEUM 



DESCRIPTION OF FIGURES 



Figure i 



Side view of large Venus mercenaria. Mantle fold on right side 

 of the body has been removed. The edge of the left fold of the 

 mantle is shown at m. The exhalent, ex. s, and inhalent, in. s, 

 siphons are modified parts of the mantle. 



Water bearing food and other floating substances enters the 

 space between the mantle folds- — the mantle chamber — through 

 the inhalent siphon. Hanging in this chamber are the foot, /, and 

 gills, og and ig. Cilia on the gills cause water to enter them, 

 forcing it to their bases, into the epibranchial chambers, ec, and 

 then backward and out of the body through the excurrent siphon. 

 This is indicated by fine, dotted arrows. The two large transverse 

 muscles — the anterior and posterior adductors — which, by their 

 contraction, close the valves of the shell, are shown at aa and pa. 



Reference letters : aa, anterior adductor muscle ; pa, posterior 

 adductor muscle; ec, epibranchial chamber; og and ig, outer and 

 inner gills ; ap and pp, anterior and posterior palps ; ex. s and in. s, 

 exhalent and inhalent siphons; /, foot; m, edge of left mantle fold; 

 s, ventral margin of shell. 



Figure 2 



Drawn to show that floating particles which -touch the surface 

 of the visceral mass are taken posteriorly and thrown off into the 

 mantle chamber at x. From this region, they are removed from 

 the body by the contraction of the adductor muscles, which dis- 

 cbarges a large part of the water in the mantle chamber. 



At pp is shown the striation of the inner side of the posterior 

 palp, over which food is taken to the mouth. The unstriated 

 margin is also shown. 



Other reference letters as in figure 1. 



Figure 3 



Paper model of lamellibranch gill. A diagrammatic figure to 

 show the basketlike structure of the gill. 



Reference letters : ic, interfilamentar connections ; p, partition 

 or septum holding the two halves of the gill together; r, a rod 

 or filament; s, space between filaments. 



