FLOUNDER-FISHES. 
363 
same genus as the ‘ Plagusia a that Steenstrup had ob- 
tained from different parts of the Atlantic. 
The most remarkable point in the appearance of 
the larva? of the Flatfishes for the first few days after j 
they have left the egg, is the elongated, almost Eel-like 
shape of the body in the majority of the species (fig. 
98) In the true Flatfishes this shape, which is deep- 
ened oid}' by the continuous vertical fin, without true 
rays, which extends from the occiput round the tip of 
the tail to the vent, may be retained until the tail has 
assumed its heterocercal form and developed true fin- 
rays. The pectoral fins have now appeared. Then the 
Fig. 99. Continuation of the changes of growth in the fry of Pleuronectes arnericanus. The body of the larvae now grows deeper, though 
chiefly owing to the more and more distinct separation of the dorsal and ventral tins from the caudal fin. a, a larva 8 mm. long, with the 
left eye moved slightly forward, which appears from its altered position, first with relation to the brain, and second with relation to the 
hind (lower) end of the upper jaw-bone. Rudiments of the hypural bones now present under the raised posterior tip of the notochord. 
I/, a rather more advanced larva, witli the left eye visible from the right side of the body, raised slightly above the nasal profile, and mov- 
ed forward to a point about 1 / 2 its own length in front of the right eye. Caudal fin rounded, and rudiments of the ventral fins visible, 
e, a larva 12 mm. long, with more distinct ventral fins and with the left eye moved still farther forward, d, with the greater part of the 
left eye visible from the right side, e , a young specimen nearly 18 mm. long, with the left eye at the dorsal margin of the head, but 
almost entirely transferred to the right side, where it has also moved slightly back, while the front part of the dorsal fin 
has begun to develop to the left of it. After A. Agassiz. 
a That these small Flatfishes belong to the group of the Sole, is hardly probable. They are most like those larvae which Raffaele 
(Mith. Zool. Stat. Neapel, Bd. VIII, p. 51, pi. 3, figs. 16 and 18) referred to the genus Arnoglossus. A true, transparent genus of Sole, 
on the other hand, or a larva thereof seems to be described by Brown-Goode (Proc. U. S. Nat. Mus. 1880, p. 344) under the name of 
Thyris pellucidus, from the deep water off Newport. 
b Sometimes the larvae are furnished with a long occipital fin-ray even in this stage: see Raffaele, 1. c., pi. 3, fig. 12, and perhaps 
Emery, the same magazine, Vol. VI, pi. 10, fig. 26. 
