. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. Limulus polypheaua, (ventral aspect.) a, carapace; b, frontal portion of the carapace; c, thorax ; d, chelifera; e,f, y, h, i,.j, legs, the basilar portions of which surround the mouth and act as mandibles ; /, under-lip ; m, branchial or lamellii'orm appendages ; n, mouth. itself under the shape of two thin and much expand- ed laminae which serve as a kind of broad operculum to cover the whole of the oral apparatus. Starting from this complication of structure, the greatest in the series, we shall see the ap- paratus de
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. Limulus polypheaua, (ventral aspect.) a, carapace; b, frontal portion of the carapace; c, thorax ; d, chelifera; e,f, y, h, i,.j, legs, the basilar portions of which surround the mouth and act as mandibles ; /, under-lip ; m, branchial or lamellii'orm appendages ; n, mouth. itself under the shape of two thin and much expand- ed laminae which serve as a kind of broad operculum to cover the whole of the oral apparatus. Starting from this complication of structure, the greatest in the series, we shall see the ap- paratus degenerating by successive degrees, at the same time that in any given group its com- position presents much less of constancy or regularity. The Sergestes among the Decapods have one pair of maxillary feet fewer than the highest number; the Edriophthalmians have no more than a single pair, whilst in the Thysanopoda and the generality of the Sto- mapoda the number of oral appendages they are terminated. The most favourable disposition to these ends is observed in the lobsters, crabs, &c.; in a word in a very great number both of the short and long-tailed De- capods, in which the anterior thoracic extre- mities terminate in pincers of greater or less strength, armed with teeth and sharp hooks which give them increased powers of pre- hension. This form results mainly from the state of extreme development in which the pe- nultimate articulation frequently occurs, and its assumption of the shape of a finger, by the prolongation of one of its inferior angles. Against the finger-like process thus produced, which is of great strength and quite immove- able, the last articulation can be brought to bear with immense force, as it is put into mo- tion by a muscular mass of great size, and in relation with the extraordinary size of the pe-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearan
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