. The Cambridge natural history. Zoology. OPHIOTHRIX MOUTH-SKELETON 483 are a pair of plates termed " peristomial ; These discs— of which there are two in each radius, one on each jaw which flanks the radius—possibly represent the separated halves of the first vertebra, the apparent first vertebra being really the second. On the flank of the jaw there is dorsally a groove for the water- A. A4 Asteroid. Fig. 211.—Diagrams to show the modification of the ambulacral and adamhulacral ossicles to form the armature of the mouth. A, Aste- roid ; B, Ophiuroid. Ai-A^ the first four amb
. The Cambridge natural history. Zoology. OPHIOTHRIX MOUTH-SKELETON 483 are a pair of plates termed " peristomial ; These discs— of which there are two in each radius, one on each jaw which flanks the radius—possibly represent the separated halves of the first vertebra, the apparent first vertebra being really the second. On the flank of the jaw there is dorsally a groove for the water- A. A4 Asteroid. Fig. 211.—Diagrams to show the modification of the ambulacral and adamhulacral ossicles to form the armature of the mouth. A, Aste- roid ; B, Ophiuroid. Ai-A^ the first four ambulacra ossicles ; Ad^-Ad^, the first four adamhulacral ossicles ; ./j, the first plate of the interradius (in the Ophiuroid the scutum buccale); P, the spines borne by the jaw (in the Ophiuroid the teeth) ; T, the torus angularis ; W, the water - vascular ring ; Wr, the radial water- vessel ; /, //, the first two pairs of tube-feet. (After Ludwig.) ^\ ^- vascular ring and nerve-ring (Fig. 212, ), and beneath this a o-roove for the first tentacle and a pore for the second, both of which spring directly from the ring-canal; below these, in most Ophiuroidea, but not in OpMothrix, there is a row of blunt triangular spines called "mouth-papillae" (Fig. 212,p^). The words "jaw" and "tooth" are misleading. There is no evidence that the jaws of a Brittle Star are ever used for crushing food, but by means of the muscles attaching them to the first. 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 Harmer, S. F. (Sidney Frederic), Sir, 1862- ed; Shipley, A. E. (Arthur Everett), Sir, 1861-1927. ed. [London, Macmillan and Co. , Limited; New York, The Macmillan Company
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
