. Zoology for high schools and colleges. Zoology. 338 ZOOLOGY. mia the shell is inequilateral, one, usually the lower, being fixed to some object, and the intestine does not pass through the ventricle; in Area the ventricle is double. In Lucina and Coriis there is but one gill on each side, and in Pecten, Spondylus and Trigonia the gills are reduced to comb-like. Pig. Wi.~^MytiUs edulis, common muesel. a, mantle; b. foot; c, byssne; d and e, muscles retracting the foot; J\ mouth ; q^ palpi ; A, visceral mass • i, inner gill; j^ outer giU.—From Brehm'e " ; processes. There
. Zoology for high schools and colleges. Zoology. 338 ZOOLOGY. mia the shell is inequilateral, one, usually the lower, being fixed to some object, and the intestine does not pass through the ventricle; in Area the ventricle is double. In Lucina and Coriis there is but one gill on each side, and in Pecten, Spondylus and Trigonia the gills are reduced to comb-like. Pig. Wi.~^MytiUs edulis, common muesel. a, mantle; b. foot; c, byssne; d and e, muscles retracting the foot; J\ mouth ; q^ palpi ; A, visceral mass • i, inner gill; j^ outer giU.—From Brehm'e " ; processes. There are usually no eyes present; in the scallop {Pecten), however, there is a row of bright shining eyes with tentacles along the edge of the mantle, and contrary to the habits of most bivalves, the scallop can skip over the surface of the water by violently opening and shutting its shell. Trigonia is also capable of leaping a short distance; while Lima (Fig. 161) is an active flyer or leaper. The Ameri- can oyster* is dicecious, while most mollusks are monoecious or hermaphroditic. The foot varies much inform; in the mussel (Mytilus, Figs. 162, 163), Pinna, Cyclocardia {Car- dita) (Fig. 164), and the pearl-oyster it is finger-shaped and * The European oyster is cleai'ly lierinnphvoditic (Ryder).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Packard, A. S. (Alpheus Spring), 1839-1905. New York, H. Holt and Company
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