144 WILLIAM RAY ALLEN. 



EXPLANATION OF PLATE II. 



FIG. 3. The inner labial palp; outer palp removed; normal ciliary streams of 

 furrowed surface. 



FIG. 4<z. (Slightly diagrammatic. See Fig. 46.) The left labial palps, adjacent 

 mantle surface, and end of gills; right mantle, gills and palps, and whole body 

 removed; showing point (X) where streams of food from gills and mantle converge 

 at the labial palps. 



Broken arrows indicate the ciliary currents of the mantle; solid arrows those of 

 the gills; and barbed arrows those of the palps. Where the broken arrows are 

 seen upon the gills they are meant to apply to the mantle just beneath. 



FIG. 46. Key to Fig. 40; all organs removed except left mantle, gills and palps; 

 the area within double lines has been enlarged as Fig. 40. 



Abbreviations. 



A, anterior, P, posterior, 



aa, anterior adductor muscle, pa, posterior adductor muscle, 



fs, furrowed surface of labial palps, r, mucous accumulations of refuse 

 gi, inner gill, material, 



go, outer gill, sc, suprabranchial chamber, 



/, lips se, excurrent siphon, 



Ip, labial palps, si, incurrent siphon, 



h, liver, sp, line of attachment of the palps 

 ma, unfurrowed margin of palps, to each other, 



ms, left mantle, X, point of convergence of ciliary 



currents near labial palps. 



