174 
ACTING PTERYGII. 
Leptotrachelus armatus, W. von der Marck. 
1863. Leptotrachelus armatus, W. von der Marck, Palseontogr. vol. xi. 
p, 59, pi. X. fig. 3. 
1885. Leptotrachelus armatus, AV. von der Marck, ibid. vol. xxxi. 
p. 260. 
Type. Imperfect fish ; Academy of Mlinster, AYestphalia. 
The type species, attaining a length of about 0'5. Length of head 
with opercular apparatus contained about six times in the total 
length to the base ef the caudal fin. Anterior abdominal region 
excessively slender, a series of about 10 anterior vertebrse equalling 
the length of the head. Pelvic fins much larger than the pectorals, 
arising at about the middle point of the trunk. Dermal scutes 
of abdominal region excessively attenuated, those of the caudal 
region robust. 
Form. 4’ Toe. Upper Cretaceous: AV'estphalia. 
F. 2109. Imperfect head and abdominal region, with remains of the 
fins ; Sendenhorst. Egerton Coll. 
Leptotrachelus triqueter, Pictet. 
1850. Dercetis triqueter, F. J. Pictet, Poiss. Foss. Mont Liban, p. 47, 
pi. ix. figs. 5, 6. 
1850. Dercetis linguifer, F. J. Pictet, ibid. p. 47, pi. ix. figs. 7, 8. 
[Fragment of abdominal region ; Geneva Museum.] 
1866. Leptotrachelus triqueter, Pictet & Humbert, Nouv. Eech. Poiss. 
Foss. Mont Liban, p. 95, pi. xiv. figs. 1, 2. 
1887. Leptotrachelus triqueter, J. W Davis, Trans, Roy. Dublin Soc. 
[2] vol. hi. p. 620, pi. xxxviii. fig. 1. 
Typ>e. Fragment of abdominal region ; Geneva Museum. 
A species attaining a length of about 0‘3. Head with opercular 
apparatus occupying about one fifth of the total length of the fish to 
the base of the caudal fin. Anterior abdominal region not exces¬ 
sively elongated, its vertebral centra about twice as long as deep, 
and a series of 16 or 17 equalling the length of the head; the other 
vertebrae nearly similar in proportions. Pectoral fins each with 
about 11 rays, the length of the longest equalling one third that of 
the head with opercular apparatus ; pelvic fins slightly larger than 
the pectorals, arising just behind the anterior third of the trunk, 
each with not less than 7 or 8 rays; dorsal fin occupying the 
middle third of the trunk, with about 35 rays, the hindermost 
comparatively small and slender ; anal fin with about 8 rays, twice 
as distant from the pelvic pair as from the caudal. Dermal scutes 
of moderate size and narrow, those on the dorsal and ventral 
borders of the caudal region bearing a backwardly-directed smooth 
