Dekmoptekes. FISHES. Petkomyzontids. 1 1 1 
support the large tootli-bearing tongue. When a 
Jly.xinoid or a Petromyzontid is preserved in spirits, 
the teeth readily flake off in cap-shaped layers, leaving 
a comparatively soft, conical nucleus, and furnishing 
evidence of the muco-dermoid origin of these organs in 
the Dermopteres. The arrangement and form of the 
labial, palatine, and lingual teeth of the difl'erent Petro- 
myzontids supply the generic characters of the various 
groups that compose the family. One Australian genus 
( Geotria) has a remarkably large guttui al pouch before 
the gill-openings, corresponding to the rudimentary 
dilatation of the same part in the common Marine 
Lamprey, and having an external resemblance to the 
goitre of the iguana. 
The single mesial nostril-tube of the Dermopteres 
is flask-shaped in the Lamprey, and descends to the 
base of the skull, but is there closed by the imperforate 
mucous lining of the palate, differing in that respect 
from the naso-palatine tube of the rnyxinoicls, which 
terminates by a valvular opening on the roof of the 
mouth. In the Lampreys, the eye-ball is supplied 
with muscles for effecting its various movements, which 
are wanting in the rudimentary optic organs of the 
myxinoids ; and, on the other hand, the acoustic cap- 
sules are less conspicuous on the base of the skull than 
in myxine, such prominence being an embryonic 
character. There is also a greater extension of the 
organ of hearing of the Lampreys into a membranous 
vestibule, a fenestrum, or as Breschet names it an 
aqueduct, and an accessary sinus, but there are neither 
semicircular canals nor otolites. The author just 
named, considers the organ of hearing in the Lam- 
preys to have a stronger resemblance to that of the 
crustaceous or cephalopode molluscs, than to the 
acoustic apparatus of osseous fishes."* None of the 
Dermopteres present a greater development of the 
hyoid apparatus, than that which consists in the presence 
of a lingual cartilage, and some ligamentous bands 
which we shall notice below, as existing in the larval 
state of some members of the group. 
A small Dermoptere, inhabiting the streams fre- 
quented by the Lampreys throughout Europe, and 
known in England under the various names of Prid, 
Pride, Sandpride, Sandburker, Stonegrig, andMudlurker, 
was ascertained by Auguste Muller some few' years ago, 
to be merely a larval condition of the Fringed Lampern. 
Its eyes are so small, that it was named the Blind 
Lamprey by the distinguished British naturalist Bay ; 
and its mouth, instead of being circular, has a horse- 
shoe shape, and cannot act as an adhesive sucker; 
but the rudiment of a future suctorial muscle is per- 
ceptible in it. Neither is the pharyngeal inspiratory 
tube as yet distinct from the oesophagus, and the gills, 
instead of being wholly adherent to the w'alls of the 
gill-chambers, have their tips free. This part of the 
structure is an approach to the free gills of the osseous 
fishes, and is suited, doubtless, to the free non-parasitic 
habits of the larva or ammoccete — so the young Lam- 
preys are now called; the appellation having been taken 
from the generic name Ammocoetes, given when the fish 
was supposed to be a distinct species, and which is trans- 
* See Recherches sur I’organe de L’ouie des Poissons par 
G. Breschet. Paris, 1838. 
lated “ mud-lurker.” In the ammoccete, then, each gill- 
sac communicates directly with the pharynx, and opens 
on the side of the neck, as we shall hereafter show to 
be the case in the Selachians. No teeth are formed in 
the mouth of the ammoccete, but very early in its 
life a valve is developed within the mouth, which 
allows the water to enter, but prevents its reflux ; and 
this muscular membrane is fringed so as to act as a 
strainer out of noxious particles. The food of the 
Pride consists chiefly of infusorial animalculse (Bacil- 
laria). Auguste Muller watched Lamperns in the 
act of spawning, secured the roe, kept it under obser- 
vation until it was hatched, and afterwards carefully 
observed the larval or ammoccete life of the 
fish. In the fourth year of its existence, he saw the 
transformation to the adult form begin, and go on to 
completion in the course of ten days. There is no 
increase of size, but in that time the respiratory 
pharyngeal tube is formed, teeth are evolved, the valve 
or velum in the mouth disappears, the intestinal canal 
is sensibly abbreviated, and the roe which was pre- 
viously transparent, becomes opaque. This transfor- 
mation, though not so remarkable externally as that 
which occurs in the Tadpoles, was, previous to Auguste 
Muller’s time, unsuspected in the class of fishes. The 
facts he have stated, has been testified too by other 
observers; and the Ammocoetes, not only of the Fringed 
Lampern, but of other European Lamperns and Lam- 
preys have been detected.* 
The following genera compose the Petromyzontid family : — 
Petromyzon, Lampetra, Geotria, Velasia, Caragola, and Mor- 
dacia, all of which are characterized by Dr. Gray in one of his 
catalogues of the Fishes in the British Museum. 
THE LAMPREY {Petromyzon marinus) — Plate 1, fig. 
2 — is the species best known, and the only one so far 
as we know, that is used in Europe as food. It is 
said to be a highly esteemed fish for the table in the 
United States of America, and has long been held 
to be a delicacy in England. Henry I. is said by 
Matthew of Paris, to have died, in 1135, at St. Denis 
le Ferment, of a sudden illness occasioned by eating 
too plentifully of lampreys, as the poet Pope is reported 
to have done in more recent times ; and Henry IV. 
is stated by Pennant, quoting from Rymer’s Foedera, 
to have granted protections to such ships as brought 
over lampreys for the table of his royal consort, 
Henry VI. contracted with William of Nantes for 
a supply to his army, whithersoever it might march, 
of lampreys to be taken betw'een the mouth of the 
Seine and Harfleur. It was anciently a custom of 
the city of Gloucester, to present the British sovereign 
with a lamprey pie. Camden, speaking of the lam- 
preys of the Severn, says, that they are finest in the 
spring, being then more tender, and that, in his time, 
the Italians prepared them for the table by drowning 
them in Cretan wine, placing a nutmeg in the mouth 
and a clove in each gill-opening, rolling them up 
spirally in the flour of filbert-nuts and crumbs of 
* Dr. M. S. Schultze has written still more recently on the 
early life of Petromyzon Planeri up to six weeks after its 
exclusion from the egg. At that age the small eye is buried 
under the skin, and the oral velum of the ammoccete is present 
instead of a separate respiratory tube, so that thus far the 
memoir confirms Auguste Muller’s observations. 
