XXI MALACOPTERYGII 553 
Pectorals low down, folding like the ventrals. | Post-temporal 
forked; the upper branch attached to the epiotic, the lower 
to the squamosal; no post-clavicle; coracoids forming together 
a ventral keel; scapular foramen between scapula and clavicle ; 
pterygials well developed, three in contact with coracoid. Ven- 
trals with 7 rays. Branchiostegal rays in moderate number (8 
to 10). Air-bladder communicating with the ear. No oviducts, 
the eggs falling into the abdominal cavity before exclusion. 
Fic. 333.—Upper (A) and posterior (B) views of skull and pectoral arch of Hyodon alosoides 
(the supratemporal removed on the left side). 40, Basioccipital ; c/, clavicle ; cor, 
coracoid ; eo, exoccipital ; eot, epiotic ; eth, ethmoid ; 7, frontal ; m, maxilla ; mcor, 
mesocoracoid ; 7, nasal; vo, opisthotic ; p, parietal ; pel, postclavicle ; pm, prae- 
maxilla ; por, praeorbital ; pff, postfrontal ; ptr, pterygials ; ptte, post-temporal ; 
sel, supraclavicle ; so, supraoccipital ; sor, suborbital ; sy, squamosal ; ste, supra- 
temporal. 
Elongate, compressed, silvery Fishes, covered with moderate- 
sized cycloid scales; head naked; mouth large, with strong den- 
tition; gill-openings wide; dorsal fin short, posterior to the 
ventrals ; anal rather elongate ; caudal well developed, forked. 
A single genus (Hyodon) with three species (Moon-Eyes of the 
Americans), all reaching the length of about a foot, inhabiting 
the fresh waters of North America east of the Rocky Mountains. 
