DERCBTIDJ!. 
173 
in length. The anterior vertebral centra are not more 
than twice as long as deep. The dermal scutes are large 
and very broad, with both the postero-lateral branches 
truncated and conspicuously ornamented with tubercles. 
The longitudinal series of scutes must have been in con- 
tact at least in the middle of the trunk ; while those of 
the lateral line are scarcely more than half as large as 
those of the dorsal row. Purchased , 1853. 
P. 3847. Remains of small head and trunk, with highly ornamented 
broad scutes ; Chalk, Kent. Enniskillen Coll. 
P. 3847 a. Portion of series of similar scutes with an ornamentation 
more radiate than usual ; Chalk, Sussex. 
Enniskillen Coll. 
The following species have been described on the evidence 
of unsatisfactory fragments, and are not represented in the Col- 
lection : — 
Dercetis limhamnensis, .1. W. Davis, Trans. Roy. Dublin Soc. [2] 
vol. iv. (1890), p. 431, pi. xlv. figs. 1, 2. Upper Cre- 
taceous (Danian) ; Limhamn, near Malmo, Sweden. 
[Imperfect head and vertebrae; Geological Museum, 
University of Lund.] 
Dercetis reussi, A. Fritsch, Rept. u. Fischo bdhm. Kreideform. 
(1878), p. 20, pi. ii. fig. 8, pi. iv. fig. 1, pi. x. figs. 1, 6, 
woodc. fig. 46. — Turonian ; Bohemia. [Fragments ; 
Royal Bohemian Museum, Prague.] 
Genus LEPTOTRACHELUS, W. von der Marck. 
[Palaeontogr. vol. xi. 1863, p. 59.] 
Syn. Triamaspis , E. D. Cope, Bull. U.S. Geol. Surv. Territ. vol. iv. 
1878, p. 67. 
External bones slightly ornamented with short ridges and rows 
of tubercles ; premaxilla longer than deep, produced to an acute 
point in front ; all the teeth small, slender, hollow cones, only 
tipped with enamel, and more or less clustered. Vertebrae between 
60 and 80 in number. Pelvic fins opposed to the dorsal, which 
does not occupy more than the middle third of the back ; anal fin 
behind the dorsal ; caudal fin forked. Most of the dormal scutes 
triradiate, some narrow heart-shaped, and adjoining longitudinal 
series scarcely if at all in contact ; a paired series along the dorsal 
and ventral borders, and another along the lateral line ; no inter- 
mediate squamation. 
