342 
SCANDINAVIAN FISHES. 
SYNENTOGrNATHI. 
Malacopterygian Eleutherognates with the lower pharyngeals united. Body covered with cycloid sccdes, the lateral 
line set low down and following a raised roiv of distinct scales along each side of the belly. Dorsal fin situated 
on the caudal part of the body, and the anal fin analogous to it in shape and position. , Ventral fins abdominal. 
Nasal cavities open. Air-bladder, when present, generally large and sometimes internally divided into cells. Pseud o- 
branchice glandular and overgrown. Branch iostegal rays generally more than 10. Digestive canal simple, straight, 
with scarcely distinguish aide stomach and without, pyloric appendages 0 . 
Even in Johannes Muller 6 this series of piscine 
forms was essentially defined, in characters and contents, 
as a distinct family, Scombresoces, or, regarded as a sub- 
order, Pharyngognathi malacopterygii. It was an extract 
from the older genus Esox of Linnaeus. and Cuvier, 
which had, however, been previously broken up, first by 
Rafinesque' and afterwards by Cuvier himself and 
Bonaparte. The last writer arranged these forms in 
two subfamilies' 6 , Belonini and Exocoetini, within the 
family of the Pikes. Cope united them 6 into a distinct 
suborder among the Physoclysts under the name of 
Synentognathi. 
In the external appearance of the body these fishes 
show a distinct resemblance to the Gray Mullets in the 
more or less broad and flat dorsal side, especially at 
the head, the greater part of which is here too, covered 
with scales. The high position of the pectoral fins also 
suggests this likeness, which is still more strongly ex- 
pressed in the structure of the skeleton. Here too, the 
skull is broad and flat at the top, with excessively large 
frontal bones and without ridges, but with the back- 
ward processes from the squa mosal bones {ossa pterotica), 
the mastoids {ossa epotica ) and the lateral occipitals well- 
developed and often elongated, as we have found them 
in Mugil. The spinous processes of the anterior ab- 
dominal vertebrae are also longitudinally** extended and 
contiguous. On the under surface of the basilar part 
of the occipital bone, sometimes in the middle as well 
as on the sides, we find downward processes resembling 
the analogous formations in the Carps. 
In the other respects, however, the Synentognates 
range themselves in sharp contrast to the Gray Mullets. 
Not only are the structure and function of the pharyn- 
geal apparatus entirely different, the upper pharyngeals 
being comparatively small, but strong and closely set 
with teeth, the lower also furnished with teeth and still 
further strengthened by their coalescence; but, in addi- 
tion to this, the straight, but fairly wide, intestinal canal, 
which, however, gradually grows narrower posteriorly, and 
is without any distinct stomach, offers the most entire 
contrast to the winding digestive canal of the Mugiloids. 
One of the most remarkable characteristics of the 
Synentognates appears in the smelling-organ. The nost- 
rils are open cavities, situated just in front of the eyes; 
and the olfactory organ itself is set on a transverse 
swelling or dermal fold that rises at the bottom of 
each cavity. 
In some of the species of the genus Hemi ramphus 
Valenciennes 7 found the air-bladder internally divided 
into cells, calling to mind the similar formations in the 
genus Amia; and Gunther, who ranged the Synento- 
gnates in close proximity to the Cyprinodontidee, grounded 
his opinion chiefly on the sexual difference, first re- 
marked by Valenciennes 5 ', in those species of the genus 
Hemi ramphus, to a great extent fresh-water fishes, which 
have subsequently been assigned by Gill 6 and Bleeker* 
to the genus Zenar chopter us. In these species, which, 
like the majority of the Cyprinodontidee, are viviparous, 
and in which the ova must, therefore, be fertilized within 
the uterus, the males are distinguished partly by a 
papilla behind the vent and partly by the advanced de- 
velopment of some of the rays of the anal fin (some- 
times of the dorsal fin as well). These rays grow longer 
and thicker than the others, and sometimes acquire 
“ According to Day the genus Scombresox possesses pyloric appendages. We have failed to find any. 
b Abh. Akad. Wiss. Berlin 1844, Phys. Abh., p. 170. 
c See Svvainson and Bleeker, 11. cc. Raeinesque’s work has not been accessible to us. 
d Nuov. Ann. Sc. Nat., Anno II, tomo IV (Bologna, 1840), p. 274. 
e Trans. Amer. Phil. Soc., Philad., N. ser., vol. XIV, pp. 456 and 457. 
f Cuv., Val., Hist. Nat. Poiss., vol. XIX, p. 3. 
( J L. c., p. 58. 
h Proc. Acad. Nat. Sc. Philad. 1863, p. 273. 
1 Ail. Ichth. Ind. Or. Ne'erl., tom. VI, p. 61. 
