enchodontim;. 
229 
Palaeontogr. vol. xx. pt. ii. (1875), p. 226, pi. xliii. figs. 
3-8. Saurodon marginatus, W. Dames, Sitzungsb. Ges. 
uaturf. Freundo Berlin, 1887, p. 77. Trichiurvhs 
(Anenchelum) marginatum, T. C. Winkler, Archiv. Mus. 
Teyler, vol. iv. (1876), p. 39, footnote. — European Chalk. 
The following specimen probably belongs to Cimolichthys, but, 
owing to the absence of the head, its identity is uncertain : — • 
38113. Type specimen of Plinthophorus robustus described and 
figured by A. Gunther, Geol. Mag. vol. i. (1864), p. 115, 
pi. vi. ; Lower Chalk, Folkestone. The characters of the 
vertebral column prove that this fish does not belong to 
the family Dercetidse, but is more closely related to the 
Enchodontidae. According to present knowledge, it thus 
seems probable that the dorsal scutes preserved in front 
of the dorsal fin are a median series ; while , the smaller 
dorsal scutes below and behind the fin are part of the 
series of the lateral line. Purchased, 1864. 
Genus PRIONOLEPIS, Egerton. 
[In Dixon, Geol. Sussex, 1850, p. 368.] 
Syn. Aspidopleurus, Pictet & Humbert, Nouv. Rech. Poiss. Foss. 
Mt. Liban, 1866, p. 107. 
Apatcopholis, A. S. Woodward, Proc. Zool. Soc. 1890 (1891), p. 634. 
Head and trunk elongate, much laterally compressed. Head 
acutely pointed, and the cranial roof exhibiting a median longi- 
tudinal depression, its lateral and occipital margins ornamented 
with ridges and tubercles of ganoine. The conical teeth irregular 
5o size, largest in the anterior part of the mandible, small and 
obtuse behind. Operculum strengthened on the inner side by a 
ridge extending horizontally backwards from tho point of suspension ; 
preoperculum narrow and deep, its lower end bearing a slender, 
posteriorly directed spine. Vertebras about 45 in number, the centra 
a t least as long as deep and constricted mesially. Paired fins 
large, the pectorals not much larger than the pelvic pair, which 
are opposed to the hinder part of the dorsal fin ; dorsal fin nearly 
median, comprising from 16 to 20 rays ; anal fin with slightly fewer 
ra }’8 than the dorsal, and much smaller ; caudal fin forked, with 
curved fulcral rays and stout, articulated, undivided rays at its 
base both above and below. Dermal scutes in one deepened series 
°n the flank, each scute overlapping its fellow and traversed above 
by the course of the lateral line. 
