HALACOZOA. TROPIOPODA. LAMELLIIiRANCHIATA. 265 



3. Venus Gallina. Hen Venus. 



Shell cordato-trigonal, moderately convex, concentrically 

 lamelloso-sulcate, with the ridges reflexed ; the frontal slope 

 short and concave, the posterior slightly convex ; the anterior 

 impression cordato-oblong, obliquely striate, the posterior 

 elongate-lanceolate ; the margins crenulate; the colour white, 

 or reddish, plain or radiated with red. Greatest length an 

 inch and a-half. 



This species varies greatly in size, form, convexity, the 

 closeness of its lamellae, and its colour. It is on this account 

 one of the most instructive, its variations affording indications 

 of similar changes in other shells. Individuals occur with the 

 shell very thick, the ridges broad and approximated or 

 crowded, or even nearly obsolete, and the colour dull white ; 

 others are of moderate thickness, with the ridges more or less 

 separated, the colour reddish or whitish, with numerous red 

 markings, and generally three radiating bands of the same 

 colour ; others are thin, more elongated, with thin distant 

 ridges, pale with radiating interrupted bands. Authors, ever 

 anxiously on the search for new species, have thus found oc- 

 casion to invent a few ; and, accordingly, the present species 

 figures at the present day, under the names of Gallina, La- 

 minosa, and rugosa, besides several more, not generally 

 adopted. On comparing a vast number of shells of these 

 alleged species, I find that they so run into each other 

 that, although as a whole the species can be easily dis- 

 tinguished, it is often impossible to say to which of the alleged 

 species an individual belongs. Our two principal varieties 

 are the following. 



A. Venus Gallina laminosa. Laminated Hen Venus. 



Shell cordato-trigonal, very thick, convex, concentricallv 

 sulcate, with the ridges reflexed, thin-edged, generally crowded 

 and imbricated, more distinct toward the umbones, where 

 their intervals are more or less marked with radiating striae ; 

 the frontal slope short and concave, with a sunk cordate, sul- 

 cate impression ; the posterior slope half as long again as the 

 anterior, somewhat convex, with the impression lanceolate, 

 smooth and glossy on the left valve, rugoso-striate and dull on 

 the other ; the muscular impressions deeply sunk, the margin 

 crenulate ; the colour dull-white, but the left side of the pos- 

 terior or dorsal impression always more or less variegated with 



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