Teeth in the upper jaw triangular, and curved; in the lower jaw longer, and more straight; all denticulated: body slender, slate-blue above.
S. glaucus, Linn. Syst. Nat. torn. i. p. 401. Watson in Phil. Trans. (1778). vol. lxviii. p. 789. pi. 12. Bloch, Ichth. pl. 86. S. cseruleus, Blainv. Faun. Franc, p. 90. Galeus glaucus, Will. Hist. Pise. p. 49. Carcharias glaucus, Flem. Brit. An. p. 167. Blue Shark, Penn. Brit. Zool. vol. iii. p. 109. Id. (Edit. 1812). vol. iii. p. 143. Le Bleu, Cuv. Reg. An. torn. ii. p. 388.
Six or seven feet. Penn. (Edit. 1812).
(Form). Elongated: the skin less rough than in the others of this genus: snout long, sharp, depressed, not pellucid at the extremity, punctured above and below with numerous pores: (mouth large, widely cleft; teeth numerous, in four or five rows; the upper ones broadest, curving a little backwards, and denticulated at the edges: the lower ones narrower, straight, in the form of a scalene triangle, and finely denticulated:) nostrils long, transverse, (equally distant from the edge of the jaw, and the extremity of the snout:) eyes elliptic, but the irides exactly circular, the pupils lenticular and transverse; (commissure of the lips extending far beyond them:) no temporal orifices: five branchial openings, (moderate, elevated, lateral; the first three largest and furthest asunder; the last two, especially the fifth, smaller, and closer together:) two dorsals; the first at about the middle of the length, excluding caudal; (triangular, of moderate size, the base longer than the two other sides:) second dorsal not far from the setting on of the caudal, (much smaller, equally triangular, and much more inclined:) anal answering to this last fin: tail (scarcely equalling half the body,) with a triangular excavation at the upper part of the base of the caudal fin; this last with two lobes, the upper extending very far beyond the lower, and terminating in an acute angle: vent at the distance of more than one-third of the length from the setting on of the caudal: pectorals large, (falciform,) very long, terminating in an acute angle: ventrals small, (cut square behind). (Colours). Back of a fine, moderately deep, blue: belly silvery. Will. and Blainv.
Said to be not uncommon on some parts of the coast, particularly that of Cornwall during the pilchard season. The specimen described by Dr. Watson in the "Philosophical Transactions" was taken on the coast of Devonshire. It is possible, however, that in the case of this species, as in that of the S. Carcharias, two or more have been confounded under one name. The above description is from Willughby, and is that of a specimen observed by him at Penzance. It appears to be the same as the S. cceruleus of Blainville, from whom I have borrowed some additional characters †. The S. glaucus of this last author is a closely allied species, in which the teeth are not denticulated at the sides.
* Borl. Cornw. p. 265.
† The parts borrowed from Blainville are included in parenthesis.
(3. Lamna, Cuv). 189. S. Comubicus, Gmel. (Porbeagle Shark).
S. Cornubicus, Gmel. Linn. torn. i. part iii. p. 1497. Turt. Brit. Faun. p. 113. Don. Brit. Fish. vol. v. pl. 108. Neill in Wern. Mem. vol. i. p. 549. Blainv. Faun. Franc, p. 96. pl. 14. f. 2.? S. Selanonus, Leach in Wern. Mem. vol. ii. p. 64. pl. 2. f. 2.? Lamna Cornubica, Flem. Brit. An. p. 168. Porbeagle, Borl. Cornw. p. 265. pl. 26. f. 4. Penn. Brit. Zool. vol. iii. p. 117. Id. (Edit. 1812). vol. iii. p. 152. Goodenough in Linn. Trans, vol. iii. p. 80. pl. 15. Le Squale Nez, Cuv. Beg. An. torn. ii. p. 389.?
Said to attain the length of from five to nine feet.
(Form). Girth (in the thickest part of a specimen three feet nine inches in length) two feet one inch: body very thick and deep, but extremely slender and flattened just at the setting on of the tail; the sides near that part distended and sloping, thinning off to a sharp angle or elevated line: snout very long, slender towards the extremity, sharp-pointed, and punctured beneath: nostrils near the mouth, at about one-fourth of the distance between it and the end of the snout; of a lunar form, the extremities pointing backwards: mouth semicircular: teeth very sharp, smooth, two-edged, with a little acute process at the base on either side; (the process in some concealed within the gums;) arranged (according to Goodenough) in the upper jaw, in two rows, except in the front, where the two middle ones stand single; in the under jaw, in two rows also, except in the front, where the two middle teeth have a triple row; the inner row bent inwards, the others all turned outwards; (according to Pennant) in three rows in the upper jaw; the same on the sides of the lower, but only two rows in the front of the latter: eyes about four inches* from the extremity of the snout, and upon an exact level with the surface of the body: branchial openings five in number, placed in a regular series; the apertures perpendicular, and about three inches long: skin, when stroked backwards, a little roughish, with an obsolete line of minute tubercles running from the head down the sides, and at length ending in the thick elevated ridge, which takes place at the depression of the body near the tail: first dorsal placed nearly in the middle, erect, its height not quite equal to its length: second dorsal pretty near the tail, much smaller: anal nearly opposite to this last, of the same length and size: above and below the tail, near the base of the caudal, a semicircular or lunar impression, the points directed backwards: caudal of a lunar form, vertical, the upper lobe nearly one-third longer (Pennant says, a little longer †) than the lower: pectorals immediately behind the branchial openings, and equalling rather more than one-sixth of the entire length; of a semilunar form behind: ventrals small, also of a semilunar form behind. Gooden. and Penn. (Colours). " Colour of the whole upper part, the sides, fins, and tail, dusky, tinged obscurely with green and blue; beneath, from the tip of the nose, and also part of the sides, entirely white." Penn.
This species was first noticed by Jago, from whose drawing of it Borlase's figure was engraved. Since his time many other individuals have occurred on different parts of the coast. Dr. Goodenough's specimen was obtained at Hastings; Pennant's at Brighton. Mr. Neill states that it is occasionally met with in the Frith of Forth: Mr. Couch remarks that on the coast of Cornwall it is not uncommon. It appears to be the same as the S. Selanonus of Leach. Is ovoviviparous. Hunts its prey (according to Mr. Couch) in companies, from which circumstance it has received its common name. Obs. Authors do not agree in all the characters which they assign to this species, but it is probable that some of these, especially the number of rows of teeth, may vary with age.
* This is with reference to Dr. Goodenough's specimen: as, however, there was only an inch difference in length between his and Pennant's, this difference would not much affect the relative proportions.
† According to Cuvier and Blainville, the lobes are nearly equal.