96 FOSSIL FISHES OF THE ENGLISH CHALK. 



allied genera were named Cladocyclus by Agassiz, who referred all the English 

 specimens to one species, Cladocyclus lewesiensis (Poiss. Foss., vol. v, pt. i, 

 1837-44, pp. 8, 103, pi. xxv<z, figs. 5, 6). Two typical examples are shown in 

 PI. XXI, figs. 5, G. They must have been relatively large, and most of them are 

 ovoid with the longer axis vertical. Their exposed portion (<?.) is a comparatively 

 small sector covered with small pits, each surrounded by a raised border. The 

 hinder edge of the scale is not crimped or serrated. The overlapped portion is 

 marked by the fine concentric lines of growth and by a few conspicuous radiating 

 grooves, which are often interrupted. 



1. Ichthyodectes minor (Egerton). Plate XIX, fig. 6 (?) ; Text-figure 23. 



1850. Hi/psodon minor, P. M. G. Egerton, in F. Dixon, Geol. Sussex, p. xiv, pi. xxxii,* fig. 9. 



1877. Ichthyodectes minor, E. T. Newton, Quart, Journ. Geol. Soc, vol. xxxiii,p. 520, pi. xxii, fig. 14. 



1901. Ichthyodectes minor, A. S. Woodward, Catal. Foss. Fishes B. M., pt. iv, p. 102. 



Type. — Imperfect mandible, probably from one of the Turonian zones ; British 

 Museum. 



Specific Characters. — A species of moderate size, with mandible about 14 cm. in 

 length. Oral border of dentary bone nearly straight, with a slight convexity 



Pig. 23. -Ichthyodectes minor (Egerton); outline of left mandibular ramus, outer aspect, two thirds 

 nat. size, restored from the two mandibular rami of the type specimen. — Chalk ; Sussex. 



towards its anterior end ; the outer face of the bone not sharply bulging outwards 

 in a longitudinal ridge; its depth at the symphysis about equal to one-quarter the 

 total length of the mandibular ramus ; teeth rather large and stout, upright and 

 straight, not curved at their apex; total number of tooth-sockets in dentary about 

 30. 



Description of Specimens. — The type specimen in the Dixon Collection exhibits 

 the greater part of both mandibular rami, the one figured in Dixon's work, the 

 other by B. T. Newton (loo. c'tt.). It forms the basis of the above diagnosis and 



