70 
ACTINOPTEEYGII. 
margin of the jaws, larger in the mandible than on the 
maxilla. The characteristic operculum, preoperculum, 
and enlarged lower cheek-plates, with a few of the 
branchiostegal rays, are also distinct in impression. 
Enniskillen Coll. 
P. 3888. Small fish ; Sendenhorst. Enniskillen Coll. 
P. 2108, P. 2108 a. Three more imperfect small specimens; Sen¬ 
denhorst. Egerton Coll. 
P. 2105. Eemains of small fish displaying some of the stout conical 
teeth clustered on one of the inner bones of the mouth; 
Sendenhorst. Some of the scales are also well preserved. 
Egerton Coll. 
35012. Scattered remains of head and abdominal region; Senden¬ 
horst. Appearances are not quite conclusive, but suggest 
that the parasphenoid is a slender toothless bone, while 
the inner clustered dentition is borne by the long and 
laminar entopterygoid. The latter element, whatever its 
nature may be, is only imperfectly preserved, but the 
hollow bases of the teeth are shown in a patch extending 
along its middle region, not reaching the borders. 
Purchased^ 1860. 
20586. Imperfect trunk displaying parts of the fins and some 
of the vertebrae in section ; Stromberg. Purchased., 1846. 
The following specimens differ from I. grandis in the comparative 
slenderness of the trunk, and are thus of the form described under 
the name of Istieus gracilis (L. Agassiz, Poiss. Poss. vol. v. 1839-44, 
pt. i. p. 13, pt. ii. p. 94, pi. XV.; F. A. E-oemer, Yerstein. iSTord- 
deutsch. Ivreidegeb. 1840, p. Ill ; W. von der Marck, Palaeontogr. 
vol. xi. 1863, p. 40, pi. v. fig. 2). The type specimen, however, 
in the Palaeontological Museum, Munich, and all others of the 
same form, seem to owe their slender proportions to distortion 
during fossilisation. 
P. 3889. Two specimens about 0'3 in length associated on one 
slab ; Sendenhorst. Enniskillen Coll. 
Istieus macro cephalus, Agassiz. 
1842-44. Istieus macrocephalus, L. Agassiz, Poiss. Foss. vol. v. pt. i. 
p. 13, pt. ii. p. 93, pi. xvi. upper fig. {noyi lower fig.). 
Type. Imperfect fish ; British Museum. 
