. A textbook of invertebrate morphology [microform]. Invertebrates; Morphology (Animals); Invertébrés; Morphologie (Animaux). ..,*^>i,..,*«i»is*^'' TYPE MOLLUaCA. 327 truded, and two posterior, the braucliial aud aual openings. The mantle around these latter frequently becomes prolonged so that two tubes, or siphons as they are termed, are formed, sometimes in contact with one another {Phohvi), sometimes quite sepairate (Venus)^ sometimes capable of n^tractiou witliiu the shell, sometimes so large as to be incapable of retraction {Myd).. Fig. 147.—.4, Mya arenarin with the siphons slightly
. A textbook of invertebrate morphology [microform]. Invertebrates; Morphology (Animals); Invertébrés; Morphologie (Animaux). ..,*^>i,..,*«i»is*^'' TYPE MOLLUaCA. 327 truded, and two posterior, the braucliial aud aual openings. The mantle around these latter frequently becomes prolonged so that two tubes, or siphons as they are termed, are formed, sometimes in contact with one another {Phohvi), sometimes quite sepairate (Venus)^ sometimes capable of n^tractiou witliiu the shell, sometimes so large as to be incapable of retraction {Myd).. Fig. 147.—.4, Mya arenarin with the siphons slightly expanded; li, iiintT sur- face of tlie right valve of the shell of Mf/a. aa = impression of anterior ad- jm = impression of posterior ad- ductor muscle. ductor muscle. I = ligament. pi = pallial line. m = mantle edge. a = siphon. p = foot. si = siphonal impression. In conformity with the form of the mantle-lobes the shell consists of two similar portions or valves, lying on the sides of the body and united along the dorsal mid-line by a hinge. The hinge is formed by a ligament, as it is termed, which is really a portion of the shell substance, and consists of an external portion continuous with the epidermis of the shell and an iuterntil elastic portion, frequently calcified to a cer- tain extent, and continuous with the middle layer (prismatic layer) of the shell. When at rest the two valves of the shell are kept apart along the ventral line by the elasticity of the hinge-ligament, and it is only by the application of force that. 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 McMurrich, J. Playfair (James Playfair), 1859-1939. New York : H. Holt
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishernewyo, bookyear1894
