[Footnote 3: This fish has a sharp round spine on the side of the body near the tail; a formidable weapon, which is generally partially concealed within a scabbard-like incision. It raises or depresses this spine at pleasure. The fish is yellow, with several nearly parallel blue stripes on the back and sides; the belly is white, the tail and fins brownish green, edged with blue. It is found in rocky places; and according to BENNETT, who has figured it in his second plate, it is named _Seweya_. It has been known, however, to all the old ichthyologists, Valentyn, Renard, Seba, Artedi, and has been named _Chætodon lineatus_, by Linné. It is scarce on the southern coast of Ceylon.] Of these richly coloured fishes the most familiar in the Indian seas are the _Pteroids_. They are well known on the coast of Africa, and thence eastward to Polynesia; but they do not extend to the west coast of America, and are utterly absent from the Atlantic. The rays of the dorsal and pectoral fins are so elongated, that when specimens were first brought to Europe it was conjectured that these fishes have the faculty of flight, and hence the specific name of "_volitans_" But this is an error, for, owing to the deep incisions between the pectoral rays, the pteroids are wholly unable to sustain themselves in the air. They are not even bold swimmers, living close to the shore and never venturing into the deep sea. Their head is ornamented with a number of filaments and cutaneous appendages, of which one over each eye and another at the angles of the mouth are the most conspicuous. Sharp spines project on the crown and on the side of the gill-apparatus, as in the other sea-perches, _Scorpæna, Serranus_, &c., of which these are only a modified and ornate form. The extraordinary expansion of their fins is not, however, accompanied by a similar development of the bones to which they are attached, simply because they appear to have no peculiar function, as in flying fishes, or in those where the spines of the fins are weapons of offence. They attain to the length of twelve inches, and to a weight of about two pounds; they live on small marine animals, and by the Singhalese the flesh (of some at least) is considered good for table. Nine or ten species are known to occur in the East Indian Seas, and of these the one figured above is, perhaps, the most common. [Illustration: PTEROIS VOLITANS.] Another species known to occur on the coasts of Ceylon is the _Scorpæna miles_, Bennett, or _Pterois miles_, Günther[1], of which Bennett has given a figure[2], but it is not altogether correct in some particulars. [Footnote 1: The fish from the Sea of Pinang, described by Dr. CANTOR with this name (Catal. Mal. Fish. p. 42), is again different, and belongs to a third species.] [Footnote 2: _Fishes of Ceylon_, Pl. ix.]