The Zoologist/3rd series, vol 1 (1877)/Issue 5/On the Occurence of the Centrine Shark off the Coast of Cornwall

by Thomas Cornish

 

ON THE OCCURRENCE OF THE CENTRINE SHARK
OFF THE COAST OF CORNWALL.

By Thomas Cornish.

 

I have recently obtained from a trawler a specimen of the Centrine Shark (Squalis centrina), the first, so far as I can ascertain, taken in English Seas. It was trawled up from a sandy bottom in twenty-six fathom water near the Wolf Lighthouse. It is at all events so rare a fish that I feel justified in giving you some account of it.

The feature which at once distinguishes the fish from all other sharks which I have seen is the presence within the skin and through the centre of the two dorsal fins of a stout spine, the end of which projects beyond the fin. The spine of the first dorsal starts from the base of the horizontal middle of the fin and inclines forward; the spine of the second dorsal starts from about the same relative position and inclines backward; so that each fin is a complete spritsail with the sprit rigged.

The length of my specimen is two feet one inch, over all (Bloch says the fish reaches a length of three or four feet). Its girth immediately before the pectorals, nine inches and four-eighths; girth behind the first dorsal, twelve inches. The head is depressed and broad. The eyes are large and long, with bright green round pupils and no nictitating membrane; over them the orbit is a strong bony ridge, and immediately behind them are blow-holes. Behind them and in front of the pectorals are five very small gill-apertures. The lips are very white and very fleshy and entirely cover the teeth. Bloch apparently described his fish from a specimen dead long enough for the fleshy lips to have dried back.

The mouth is very small. The teeth in the lower jaw are equilateral and in two rows, the outer one consisting of much smaller take than the inner one. The teeth in the upper jaw are numerous and in irregular rows and sharp-pointed, and I think all of them are serrated, but they are all so small that I am not certain about this. The first dorsal stands just over the pectorals, and the second just over the ventrals, and each dorsal has through it the spine I have described, and is free at the rear of the base for about half an inch. The belly is broad and flat; the pectorals and ventrals lie flat out from it, and between them on each side there is a strong cartilaginous ridge, forming—with a similar one across between the pectorals—a flat space resembling the belly of the Monk (or Angel-fish), but harder.

The ventrals are distinct, and on the inner side of each is a rudimentary clasper. There are no anals, and the caudal is single-lobed, except that just where the fleshy part ends there is a slight indentation. The nostrils are large, underneath the snout, in advance of the mouth, and divided into two lobes each by two cutaneous flaps overlapping each other. Within is visible a very delicate membrane, something of the shape of a fern-leaf or the back-bone of a sole. The lateral line starts from the extremity of the nozzle, passes over the orbit of the eyes in a pale broad line down the side with a slight curve, and is entirely lost just behind the second dorsal.

The colour is dark cinereous in blotches over the back, and light cinereous on the belly, and the skin is the roughest I ever saw on any shark. The dorsals are very long and high. The first dorsal in my specimen is four inches and a half long at the base, three inches and four-eighths high at its extreme rear (where it is highest), and the spine is two inches and seven-eighths long; and the second dorsal, just five inches to the rear of the first, is nearly about the same size. As I have said, these large standing dorsals at once distinguish the fish, and if it ever gets common enough to require an English name it should be called the Spritsail Shark. Bloch mentions it as a Mediterranean species, and also as occurring in France, in the Northern Ocean, but I do not understand whether, by the Northern Ocean, he refers to the English Channel or the North Sea. My specimen is in the hands of Mr. Vingoe for preservation.

[The occurrence of Squalis centrina on the British coast is a new and highly interesting fact. This shark is an inhabitant of considerable depths, and is not uncommon in the Mediterranean, but we believe has not hitherto been found further north than the latitude of Lisbon. It is to be hoped that this important specimen will be well preserved and deposited in some public Museum.—Ed.]