[103] FLOUNDERS AND- SOLES. 327 
of the genus. If its scales are really keeled it may form the type of a 
distinct genus. The increased number of fin-rays also indicates a 
probability that the number of vertebre will be found to be similarly 
increased. For the subgenus of which this is the type, we have sug- 
gested the name of Acedia. 
LARVAL FORMS. 
(BIBRoNIE. ) 
The very young of all the Plewronectide so far as known are trans- 
parent and with the eyes symmetrical. Ata length of from one-fourth 
of an inch to an inch the eye of one side moves by degrees to the other 
side, where it becomes the upper eye. The question has been much 
discussed as to how this change comes about—whether by a twisting 
of the head so that the eye moves over the line of the profile, whether 
by passing from side to side beneath the frontal bone, or by passing 
between the frontal bone and the bases of the dorsal rays, or whether 
by each of these methods in different genera. The present writers have 
had no opportunity to make any observations on this point, the state- 
ments which follow being entirely. drawn from others, chiefly from the 
papers of Dr. Luigi Facciola.* 
According to Prof. Japetus Steenstrup,t who has examined some 
“‘ plagusiiform” specimens (Symphurus?) about 25 millimeters in length, 
the eye, by acombined movement of rotation and translation, goes from 
its original position to the other side by passing under the frontal bone. 
In other flounders examined by Prof. Alexander Agassiz the éye 
is said to have crossed from side to side above the frontal bone, pene- 
trating the space between this bone and the dorsal fin by sinking into 
the tissues of the head. In the species examined by Dr. Facciola the 
eye was found to pass between the frontal bone and the dorsal rays, 
but without penetrating any tissues. During the passage of the eye 
the first dorsal ray formed a projection detached from the cranium, and 
in the notch between this and the head the eye has passed from one side 
to the other. 
It has not been easy to determine with certainty the species to which 
these larval forms belong. The first of these which were known were 
described by Cocco as distinct genera, allied to the flounders, but dis- ~ 
tinguished from them by the symmetrical arrangement of the eyes. 
For the group thus defined Bonaparte has proposed the family name 
of Bibronidi (bibroniide), and this name has been adopted by some of 
the Italian ichthyologists. 
vi, 1887, and ‘‘Su di Alcuni Rari Pleuronettidi del mare di Messina, ” Nat. Sicil., iv, 
1885. 
t “Om Skjebheden hos Flynderne og navnlig om Vandringen af det Svre Oie fra 
Blindsiden til Ojesiden tvers igjennem Hovedet,” 1864. 
