OCR Text |
Show 714 MR. J. Y. JOHNSON ON A N E W S H A R K . [June 2 7 concave between the eyes and spout-holes ; cheeks convex ; snout short, rounded in front, flat above and below. Nostrils large, reaching to the sides of the snout. Eye-slit almond-shaped. Spout-holes transversely oval, placed above the eyes. Mouth wide; the jaws slightly but evenly convex; the upper jaw protrusile from beneath the scaly skin. The slit or groove at the commissure advances to the vertical from the middle of the eye, leaving a considerable space between the opposite grooves. The posterior part of the slit is very shallow, and does not extend beyond the vertical from the posterior edge of the spout-holes. The teeth of the upper jaw are composed of sharp narrow upright conico-compressed cusps on subquadrate bases; and several rows of them are in use at once. In the lower jaw there are two rows of teeth, formed of broad flattened cusps on subquadrate bases, which have a ridge down the middle. The cusps, as the teeth approach the back of the mouth, become more and more inclined backwards, but their apices bend upwards and form an acute point; thus only part of one edge of the cusp presents an incisorial edge, at the middle of the lower jaw, having both its sides in front of the adjacent teeth, lt is formed of an upright equilateral cusp with acute edges placed on a quadrate base. The five branchial openings are large, and are situate in front of the pectoral fin, the hindmost embracing the anterior part of the root of that fin. All the fins are clothed with scales. The first dorsal fin is nearer to the pectoral fin than to the ventral fins, and has in its front part a strong spine more than half as high as the fin, which is so much worn in the specimen that its shape cannot be accurately stated. The second dorsal fin is rounded in front, where it is higher than the anterior fin. It is also armed with a strong spine (which, however, is not quite so large as the spine of the first dorsal), and it is acuminate behind and prolonged in a direction nearly parallel with the tail. The ventral fins have two-thirds of the total length of the fish in front of them. Their anterior angles are rounded off, their posterior angles prolonged and pointed. The caudal fin is shaped much like that of the true Centrophori. The tail bends upwards inside the upper lobe, and the lower lobe is well developed. The upperside of the tail behind the dorsal fin is concave. The lateral line is high up on the side of the body and straight. The claspers are furnished with a slender spine. The scutella or scales are stalked, and have subrotund laminae continuous with their stalks, each lamina being marked by two lateral and a median crest, which projects behind as an equilateral tooth. The hinder edge of the lamina is minutely serrulate. The species is named in compliment to Professor Anguste Dumeril of the Jardin des Plantes, Paris, the author of a valuable work describing the known genera and species of Sharks. The dimensions of the single example obtained (which has been added to the collection of the British Museum) are given below. |