138 



FOSSTL FISHES OF THE ENGLISH CHALK. 



Type. — Imperfect jaws ; British Museum. 



Specific Characters. — Teeth of upper jaw slightly curved; those of dentary in 

 t wo longitudinal series. 



Description of Specimens. — This species is known only by fragments of jaws, 

 which were originally referred to the Dercetid genus Stratodus, before the affinities 

 of the latter were discovered. 1 The pieces of bone are remarkably thin and 

 covered externally with a greenish-grey film. One long bone of the upper jaw, 

 measuring 12 cm. in length, bears a dense cluster of the characteristic teeth 

 (PI. XXIX, fig. 1) from end to end. The anterior part of a dentary bone (fig. 2), 

 which tapers to a blunt symphysis, exhibits the bases of attachment of two 

 regular longitudinal series of similar teeth. The outer face of this bone is 

 sculptured with a few irregular longitudinal grooves. 



Horizon and Localities. — Zone of Holaster subglobosus : Glynde and Southeram, 

 near Lewes, Sussex, 



Family Tomognathidji. 



An imperfectly definable extinct family, known only by skulls and other frag- 

 mentary remains from the Chalk. External head-bones somewhat thickened ; 



Fig. 40. Astronesthes niger, Richardson ; about two thirds nat. size. — A Stomiatid fish existing in 

 the Atlantic Ocean. After Goode and Bean. 



supraoccipital very prominent and large, extending forwards and separating the 

 parietals; ethmoidal region very short. Premaxilla and maxilla both entering 

 the upper border of the mouth, the maxilla loose and with not more than one 

 narrow supramaxilla ; dentition powerful on margin of jaws. Opercular appa- 

 ratus complete, but few branchiostegal rays and no gular plate. 



In some respects the skull and dentition of Tomognathus are suggestive of 

 those of the Stomiatidre and their allies, which exist in the deep sea (Text-fig. 40). 



1 A. Stewart, " Teleosts of the Upper Cretaceous," Univ. Geol. Surv. Kansas, vol. vi, Palffiont., 

 pt. ii (1900), p. 327, pi. lx, pi. lxi, fig. 1. Also A. S. Woodward, Catal. Foss. Fishes B M, pi iv 

 (1901), p. 188. 



