



Millimeters 



Figure 104. — Labial palps of C virginica. The mantle hood is cut off at the midrlle, and the sides are pulled aside to 

 expose the lips and the mouth. Drawn from life. h. — hood; I.g. — lateral gutter; 1.1. — lower lip; m. — mouth; 

 r.i.p. — right inner palp; r.o.p. — right outer palp; u.l. — upper lip. 



the shape and size of the cells of tlie two sides 

 of the palp is clearly seen in this figure. 



Thin and transparent cuticle covers the epithe- 

 lium of the ridged surfaces. The cilia are robust, 

 ranging in length from 8 ^ in the grooves to 20 n 

 on the tips of the ridges, with the longest cilia 

 found near the free edge of the palps. Mucous 

 cells are present but are less abundant than on 

 the smooth side. 



The ridges themselves are set at an acute angle 



to the surface of the palp and recline toward its 

 free edge. There is a noticeable difference in the 

 epithelium of the two sides of the same ridge. 

 Tlie cells lining the sides which face the mouth 

 (lower sides of ridges in figure 106) have longer 

 cilia, and tlie entire epithelium is slightly ruffled. 

 On the <ipposite sides the ciliated cells are uniform 

 and have smaller cilia. This difference appears 

 on a tangential section of the palp shown in 

 figure 107. 



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FISH AND WILDLIFE SERVICE 



