History of British animals - University of Guam Marine Laboratory

Petromyzon. FISHES. CHONDROPT. 163CHONDROPTERYGIOUS FISHES.Gen. I. PETROMYZON. Lamprey. — Maxillary ring,armed with teeth. Mouth ovate, longitudinal.— 1. P. marinus. Sea-Lamprey. Marbled with black, brown,and yellow.The second dorsal and caudal fins disjoined.— Will. Ich. 105. P. mar. Linn.Lampetra, Merr. Pin. 188—L. Rondeletii,—Syst. i. 394. Penn. Brit. Zool. iii. 76. E, Lamprey Eel ; W, Llysowenbendol In the sea and largerivers frequent.between two and three feet. Body of nearly equal thickness to theLengthfirst dorsal-fin, when it decreases suddenly to the tail. Head rounded anteally,with a slight constriction over the eyes, and rather less than the body.The first dorsal-fin semicircular in its outline. The second rises gradually alittle behind the former ; and, after reaching its greatest breadth, somewhatsuddenly, it gradually diminishes towards the tail. The tail is rounded ; therays at the end are short ; and, on the under side, from opposite the seconddorsal-fin, there is a ridge continued to the anus. Eyes lateral, in a smallcavity in front of the gill-openings. Nostril, or short tube, situate in themiddle, on the hind head. The sucker is a narrow border, surrounding thelips, consisting of an outer row of conical papilla?, and several inner rows ofshort, compressed, digitated, fringed processes. Secondary or moveable teeth,short, conical, or bifid, disposed in diverging and concentric rows. Primaryteeth two ; the one above, consisting of two contiguous processes ; the one belowlarger, lunate, with seven conical processes. Tongue small, with severalrows of small teeth. Gullet short ; the alimentary canal simple. The gillopeningsare seven on each side, ovate, transverse, having, on the ventralside, a minute tooth-like process.The cavities of the gills are lenticular,placed nearly vertically, having the gills disposed in ridges, in the directionof the apertures. The central apertures open into a common duct, by whichthe water entering from the mouth reaches the gills. It is probable, however,that while the animal isadhering to any object, and the mouth closed, waterreaches the gills directly through the lateral or external openings. The hermaphroditismof this fish has been ponited out by Sir Everard Home, Phil.Trans. 1815, 266. The lamprey leaves the sea, its ordinary residence, andenters the larger rivers, during the spring months, for the purpose of spawning.The fish, when in season, is esteemed delicious.2. P.JluviatiUs. River Lamprey.— Dusky blue above, beneathsilvery.The second dorsal-iin angular, and continuouswith the tail fin.Lampetra fluviatilis, Merr. Pin. 188— Lampetra, Sibb. Scot. 25— Will.Ich. 104 P. fluv. Linn. Syst. Nat. i. 394. Penn. Brit. ZooL iii. 79.—E, Lampern, Lesser Lamprey ; £, Nine-eyed eel ; W, Lleprog—Inrivers and the sea.Length about 10 inches. The first dorsal-fin is angular, and remote fronithe second. The secondary teeth are less numerous than in the lamprey ;but, in the absence of specimens, at present, it would be difficult to say moreon the armature of the mouth, without running great risk of error, especiallyas the descriptions of Artedi, Pennant, Bloch, Lacepede, and Donovan (whichI have consulted), differ widely from one another. It is probable, that theL 2