ACTINOPTERYcll. 109 



The Amiidae proper, without fin-fulcra, are first undoubtedly 

 represented by Megalurus in the Lower Kimmeridgian of 

 Bavaria and the Dept. Ain, France, and in the Purbeck Beds of 

 Dorsetshire. So far as known, this fish only differs from Amia 

 in the comparative shortness of the dorsal fin, and Amiopsis 

 from the Cretaceous of Istria cannot yet be distinguished from 

 it. Species of the existing genus Amia or of a fish exhibiting 

 only minor differences in the dentition occur in the Lower 

 Tertiaries both of Europe and North America. Characteristic 

 vertebrae are found in the Upper Eocene (Oligocene) of Hamp- 

 shire and the Isle of Wight, and nearly complete fishes are 

 known from the Upper Eocene of Montmartre, Paris, the Lower 

 Miocene of Kutschlin, Bohemia, and the Lower Miocene lignite 

 of central France. The genus seems to have disappeared from 

 Europe before the deposition of the Upper Miocene strata. 



The Pachycormidae are a family of Amioid fishes as com- 

 pletely adapted for a predaceous life in the open sea as the 

 modern sword-fishes. The ethmoidal region is more or less 

 produced in front of the mouth, and the premaxillae are fixed 

 to it without meeting in the middle line anteriorly. The 

 cheek is covered with plates, and the opercular apparatus is 

 complete, with numerous branchiostegal rays and a large gular 

 plate. The notochord must have been persistent, and the 

 ossifications in its sheath are feeble or absent; the vertebral 

 arches are very slender and numerous, often only superficially 

 calcified. Fin-fulcra are rudimentary or absent ; the pectoral 

 fins are long and narrow with closely apposed rays ; and the 

 caudal fin is always deeply forked. The scales are thin, small, 

 and deeply overlapping, or sometimes wanting. The least- 

 specialized genera and Pachycormus are confined to the Lias. 

 Hypsocormus, with a more prominent snout, is Upper Jurassic. 

 Protosphyrcena, with a still longer snout, is Cretaceous. 



Pachyconnus. This is an irregularly fusiform fish, with very narrow 

 caudal pedicle, very deeply forked tail, sickle-shaped pectoral fins, no 

 pelvic tins, short dorsal and anal tins (the former in advance of the 

 latter), and small scales entirely covering the trunk. The bones of the 

 cranial roof seem to be fused into a continuous shield, covered with a 

 very fine granular ornament ; and the median occipital portion is sharply 



