This section is from the book "A Manual Of British Vertebrate Animals", by Leonard Jenyns. Also available from Amazon: A Manual Of British Vertebrate Animals.
No denticulations on the preopercle, or spines on the opercle: palate without teeth: mouth not protractile: body oval, covered with large scales; no scales on the vertical fins.
Sides of the jaws furnished with rounded molars forming a pavement: cheeks scaly: a single dorsal: branchiostegous membrane with five or six rays.
(I. Chrysophrys). From four to six conical incisors in each jaw; molars large, in three or more rows.
(2. Pagrus). Conical incisors in front, with card-like teeth behind; molars of moderate size, in only two rows.
(3. Pagellus). All the anterior teeth fine and card-like: molars small, in two or more rows.
All the teeth conical, and forming but a single row; some of the anterior ones longer than the others, and hooked: cheeks scaly: a single dorsal: branch-iostegous membrane with six rays.
All the teeth card-like, and crowded together; the anterior row larger, and more hooked, than the others: cheeks scaly: branchiostegous membrane with six rays.
Body compressed; scaly: dorsal and anal fins, or at least their soft portions, closely covered with scales.
Both jaws, as well as the palatine bones, with card-like teeth: dorsal and anal fins long: the spinous rays few in number: branchiostegous membrane with seven rays.
Opercular pieces without denticulations: scales very small: body smooth: vertical fins not scaly.
Lateral line unarmed: two dorsals; the first continuous; posterior rays of the second, as well as the corresponding rays of the anal, separated into spurious finlets: body fusiform: branchiostegous membrane with seven rays.
(1. Scqmber). First dorsal separated from the second by a wide space: scales small, and every-where uniform: sides of the tail with two small cutaneous ridges.
(2. Thynnus). First dorsal reaching nearly to the second: some large scales surrounding the thorax, forming a corselet: sides of the tail with a cartilaginous keel between two small cutaneous ridges.
Lateral line unarmed: a single dorsal, continuous: body elongated; the snout produced into a sword-like process: jaws without teeth: sides of the tail with a strong projecting keel: ventrals wanting.
Lateral line unarmed: spines of the first dorsal free, and not connected by a membrane: ventrals always present.
(1. Naucrates). Body fusiform: sides of the tail keeled: two free spines before the anal.
(Lichia). Body compressed: sides of the tail not keeled: two free spines before the anal: before the spines on the back, a reclined spine directed forwards.
Lateral line armed with large, imbricated, spinous plates: two distinct dorsals; before the first a sharp reclined spine directed forwards: some free spines before the anal; sometimes connected, forming a small fin: body fusiform.
One dorsal; the spinous and soft portions separated by a deep notch: body oval, compressed: mouth very protractile: teeth small, few in number: ventrals thoracic.
(1. Zeus). Dorsal spines accompanied by filamentous prolongations of the membrane: a series of forked spines along the base of the dorsal and anal.
(2. Capros). No spines at the base of the dorsal and anal fins: body covered with rough scales.
Dorsal entire, very much elevated anteriorly: anal also elevated, with one small spine in front of the base: body oval, compressed: no teeth: ventrals, and lobes of the caudal, very much elongated; the former abdominal, with ten rays: sides of the tail keeled.
Body compressed, elongated: upper part of the head presenting a sharp edge: one dorsal running the whole length of the back; all the rays nearly equally flexible, but the anterior ones not articulated: branchiostegous membrane with seven rays.
(1. Centrolophus). Head oblong: palate destitute of teeth: a space without rays between the occiput and commencement of the dorsal.
Body very much elongated, as well as compressed: scales small.
* Snout elongated: gape wide: teeth strong, sharp, and cutting: lower jaw projecting.
Ventrals reduced to two small scales: dorsal extending throughout the whole length: anal narrow: caudal well formed: branchiostegous membrane with eight rays.
Ventrals and caudal wanting: tail produced into a long, slender, compressed filament: anal represented by a series of small, almost invisible, spines: branchiostegous membrane with seven rays.
** Mouth small, very protractile: teeth small.
Anal entirely wanting: dorsal long; the anterior rays prolonged: ventrals very long (but easily broken): caudal of few rays, attached vertically to the extremity of the tail, which terminates in a small hook or claw: branchiostegous membrane with six rays.
*** Snout very short; gape oblique: teeth well developed.
Dorsal and anal long, both reaching to the base of the caudal: ventrals moderately developed: branchiostegous membrane with six rays.
Body oval, approaching to cylindric; covered with large scales: snout very short: mouth transverse, angular when closed, the lower jaw with an eminence in the middle fitting into a corresponding hollow in the upper: teeth extremely minute: two dorsals widely separated: ventrals a little behind the pectorals: branchiostegous membrane with six rays.
Body elongated: mouth very protractile: teeth minute: two dorsals widely separate: ventrals behind the pectorals: branchiostegous membrane with six rays: a broad silver band along each side.
Body elongated: one or two dorsals: the spinous rays always slender and flexible.
Ventrals before the pectorals, very much reduced: body elongated, compressed, smooth, covered with small scales: gill-opening large; the membrane continued across the breast: a single dorsal, composed almost entirely of simple flexible rays.
(I. Blennius). Teeth long, even, close-set, forming a single row; the last in the series sometimes longer than the others, and curved: ventrals of two or three rays.
(2. Gunnellus). Teeth short, in more than one row: ventrals extremely small, reduced nearly to a single ray: dorsal ex-* tending the whole length; all the rays simple, and without articulations.
Ventrals before the pectorals, small, with three rays: body elongated, covered with a mucous secretion: branchiostegous membrane with six rays; not continued across the breast: teeth conical, in one row at the sides of the jaws, in many in front: fins invested with a thick skin; the dorsal, anal, and caudal, united; all the rays of the dorsal soft and articulated.
* Cuvier places this genus between the Mugilidce and the Gobiadce, observing that it will not exactly associate with either.
† This genus has been probably misplaced by authors. It seems (as Nilsson observes) to shew more affinity to the Malacopterygian Fishes, especially to some of the Gadidce. It is a curious circumstance that the Zoarces viviparus and the Lota vulgaris should have obtained the same English name (that of Eel-Pout,) in some parts of the country.
Ventrals wanting: body elongated, smooth: one dorsal, composed entirely of simple rays, not connected with the caudal: branchiostegous membrane with six rays: palatines, vomer, and mandibles, armed with large osseous tubercles; the anterior teeth long, and conical.
Ventrals thoracic; more or less united at the edges, forming a funnel-shaped cavity: body elongated, scaly: head moderate: gill-opening small; branchiostegous membrane with iive rays: two distinct dorsals; the first with the spines extremely flexible.
Ventrals jugular, widely separate, broader than the pectorals: body naked: head broad and depressed: gill-opening reduced to a small hole on each side of the nape: preopercle terminating behind in several small spines: two dorsals.
Bones of the carpus elongated, forming a kind of arm supporting the pectorals: skeleton semicartilaginous.
Ventrals before the pectorals: opercle and branchiostegous rays enveloped in the skin; the branchiostegous membrane forming a large purse-like cavity in the axilla: two distinct dorsals; in front of which are sonje free rays, produced into long slender filaments: skin naked: head broad and depressed; extremely large with respect to the rest of the body.
Body oblong, scaly: only one dorsal; the spines invested with membranous shreds, extending beyond their tips, and giving them a bifid appearance: lips fleshy: pharyn-geans three in number; two above and one below; all armed with strong teeth.
Lips double: branchiostegous membrane with from four to six rays: maxillary teeth conical; the anterior ones longest: pharyngeans cylindrical, blunt, forming a pavement.
(1. Labrus). Preopercle with the margin entire: cheeks and opercle scaly: first dorsal spines not elongated.
(Lachnolaimus). First dorsal spines produced into long flexible threads.
(2. Julis). First dorsal spines elongated: head entirely smooth, and without scales.
(3. Crenilabrus). Preopercle with the margin denticulated: cheeks and opercle scaly.
Mouth at the extremity of a long tube, formed by a prolongation of the rostral and opercular bones.
Body oblong-oval, compressed at the sides, carinated beneath: mouth extremely small, cleft obliquely: branchiostegous membrane with two or three slender rays: two dorsals; the anterior one placed very backward, with the first spine much longer and stouter than the others: ventrals small, behind the pectorals.
 
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