HALEC. 



51 



Type. — Imperfect fish from one of the Turonian zones ; Willett Collection, 

 Brighton Museum. 



82)ecific Characters. — The type species of the so-called PoniognatJi/ns, attaining a 

 length of al)out 40 cm. Length of head with opercular apparatus much exceeding 

 the maximum depth of the trunk, which is probably contained about four times in 

 the length from the pectoral arch to the base of the caudal fin. Length of 

 mandible somewhat exceeding the depth of the head at the occiput ; maxilla with 

 5 to 7 well-spaced teeth ; operculum considerably deeper than broad ; the infero- 

 posterior spine of the preoperculum short, stout, and ornamented with tubercles. 

 The external tubercular ornament very fine, arranged in more or less radiating 

 lines on the sides of the cranial roof, the supramaxilla, mandible, opercular 

 apparatus, clavicle, supraclavicle, and part of the post- temporal. The stouter rays 

 of the paired and dorsal fins also ornamented with longitudinal series of very fine 

 tubercles. Vertebrae about 45 in numljer. 



Description of Specimens. — The type specimen in the Brighton Museum 



ecnt- 



Fig. 11. Halec eupterygius (Dixon) ; diagram of jaws, left side, outer aspect. — English Chalk. 

 d., dentary; ccpt., ectopterygoid ; mx., maxilla; pi., palatine; pmx., premaxilla; smx., supra- 

 maxilla ; t., some inner mandibular teeth. 



(Willett Collection, no. 37) is an imperfect and slightly distorted fish, exhibiting 

 nearly all the essential characters of the genus and species. A considerably 

 smaller specimen in the British Museum (no. 43388), which is not distorted, affords 

 additional information concerning the vertebral column and the proportions of the 

 trunk. The two fossils together justify the specific diagnosis just given. 



The characters of the skull are shown by the three specimens represented 

 in PI. XIII, figs. 2, 3, 4, by the type, and by numerous other more or less frag- 

 mentary fossils. The maximum width of the craniiun, between the hinder part of 

 the orbits, equals about half its total length. The ejnotic bones (fig. 3, epo.) 

 project considerably backwards, so that the middle of the occipital border, Avhen 

 viewed from above, is observed to be excavated by a sharp re-entering angle. The 

 small posterior median crest of the supraoccipital (.socr.) extends backwards from 



