. The Cambridge natural history. Zoology. ZYGOPHIURAE 499. corpuscles, carrying haemoglobin,^ the respiratory value of which compensates for the loss of the genital bursae, which have entirely disappeared. Ophiopholis is distinguished from the foregoing genera by the granular covering of its dorsal plates; whilst in Ophiacantha these granules develop into prominent spinelets, and the arm- spines are also thorny. Ophiopholis aculeata occurs in swarms in the branches of the Firth of Clyde, and presents a most remarkable series of variations in colour. Ophiopsila is a closely allied form, disting
. The Cambridge natural history. Zoology. ZYGOPHIURAE 499. corpuscles, carrying haemoglobin,^ the respiratory value of which compensates for the loss of the genital bursae, which have entirely disappeared. Ophiopholis is distinguished from the foregoing genera by the granular covering of its dorsal plates; whilst in Ophiacantha these granules develop into prominent spinelets, and the arm- spines are also thorny. Ophiopholis aculeata occurs in swarms in the branches of the Firth of Clyde, and presents a most remarkable series of variations in colour. Ophiopsila is a closely allied form, distinguished by its large peristomial plates. Fam. 3. Ophiocomidae. —Both mouth-papillae and tooth-papillae are present; ^ the arm-spines are smooth, and the disc is covered with granules. Ophiocoma nigra is the only common British representative of this family. In this species the plates of the dorsal surface are completely hidden from view by a covering of granules. Ophiarachna. Fam. 4. Ophiothricidae.—Tooth-papillae alone present, mouth-papillae absent; arm-spines roughened or thorny. This family is represented only by OpMothrix fragilis, which is perhaps the most abundant of all British Ophiuroids, and has been selected as the type for special description. The back is covered with spinules, having, however, the triangular radial plates bare. This produces a contrast-effect, which suggested the name pentaphyllum, formerly used by some naturalists for the species. It occurs in swarms, and presents variations in colour nearly as marked as those of Ophiopholis. Fig. 221.—Oral view of Ophiacantha chelys. X4. (From Wyville Thomson.) ' Cuenot, "Etudes Morphologiques sur les Echuiodermes," ^rcA. Biologie, xi. 1891, pp. 568 et seq. -- This type of mouth-frame is represented in Fig. 215, A, by a figure of OphioscoUx, which belongs to the Please note that these images are extracted from scanned page images that may have been digitally enhanced for readabilit
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