Lectures on the comparative anatomy and physiology of the invertebrate animals : delivered at the Royal College of Surgeons . ion of the principal organic characters of this order,which is called Tetrabranchiata, and to a brief review of the extinctchambered siphoniferous shells, and of their relations to the existingCephalopods. The soft parts of the pearly Nautilus {Jig. 214.) form an oblongmass divided by an irregular transverse constriction into two nearlyequal segments; the posterior is smoothly rounded, soft, and membra-nous, containing the viscera, and adapted to the last chamber of the
Lectures on the comparative anatomy and physiology of the invertebrate animals : delivered at the Royal College of Surgeons . ion of the principal organic characters of this order,which is called Tetrabranchiata, and to a brief review of the extinctchambered siphoniferous shells, and of their relations to the existingCephalopods. The soft parts of the pearly Nautilus {Jig. 214.) form an oblongmass divided by an irregular transverse constriction into two nearlyequal segments; the posterior is smoothly rounded, soft, and membra-nous, containing the viscera, and adapted to the last chamber of theshell; the anterior is densely muscular, and includes the organs ofsense and locomotion. The mantle is very thin upon the posterior part of the body; it iscontinued backwards in the form of a slender tube, which penetratesthe calcareous siphon (c), in the septum closing the occupied chamberbehind, and is thence continued, as the membranous siphon {d)through all the other divisions of the shell to the central nucleus. Asthe mantle advances towards the anterior part of the abdomen, it in- * CCCLXXXVII. 579. Nautilus Pompilius. creases in thickness, becomes more muscular, and extends freely out-wards, forming a wide concave fold on the dorsal aspect (e), which isreflected over the black-stained involuted convexity of the shell. Themargin or collar of the mantle is continued downwards and forwardson each side with a sinuous outline, and is perforated below for thepassage of the muscular expiratory and excretory tube called thefunnel (i). Besides the muscularity of the free border of the mantle,which indicates its power of extension and contraction, its surface isstudded with the orifices of many minute glandular crypts ; and it isthe organ by which the growth of the shell is principally nidamental glands form, in the female, two circular convexitieson the ventral surface of the abdomen, behind which the mantle isencircled by a thin layer of brown matter
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Keywords: ., bookauthorowenrichard18041892, bookcentury1800, bookdecade1850
