112 
A.CTIXOPTERYGII. 
suboperculum is both broad and remarkably long. The 
teeth are partly acuminate, partly round; but it is 
probable that most of the latter owe their form to wear. 
The principal flank-scales are serrated, and the fluted 
structure is shown in all the scales from which the 
enamelled surface has been removed. Purchased , 1886. 
20673 a. A much crushed and abraded head, with the anterior 
portion of the abdominal region, the type specimen of the 
so-called L.fittoni, figured .by Agassiz, tom. cit. pi. xxx. a. 
fig. 1; Highfure, Billingshurst. The mandibular rami 
differ from those of the preceding specimen in having 
their inferior margin considerably curved downwards to a 
point at the symphysis. The openings in the scales of 
the dorsal region for sensory canals are not very regularly 
arranged. Presented by P. J. Martin, Esq., 1846. 
43073. A much more imperfect, crushed specimen ; East Grinstead. 
Purchased, 1871. 
P. 6933. Fine example of the head and anterior abdominal region of 
a young individual, shown of one-half the natural size from 
the superior (A) and left lateral ( h ) aspects in the accom¬ 
panying fig. 23; Hastings. The extremity of the snout 
is broken away, and only a doubtful fragment of bone 
appears to represent the maxilla (mcc.) on the left side. 
The cranial roof-bones are in part coarsely rugose and 
ornamented with very fine tuberculations, mostly in radi¬ 
ating lines ; the supratemporal plates ( s.t .) are arranged in 
four pairs, the two innermost not quite symmetrical and 
representing the single pair in adults. The mandible is 
shown, partly smooth, partly with the characteristic coarse 
rugosity; and the inferior border of the dentary bone (cl.) 
is very sharply curved downwards to a point at the 
mandibular symphysis. The circumorbital (c.o.), sub¬ 
orbital (s.o.), and opercular bones are well preserved on 
the left side; the first two series marked with a few 
large tubercles in their lower portion, more delicately 
ornamented above, and the opercular bones very finely 
granulated. The maximum width of the operculum (op.) 
is two-thirds as great as its depth, and its anterior margin 
is sinuous, exhibiting a considerable concavity above ; 
the maximum depth of the suboperculum (s.ojo.) is about 
half that of the operculum, and its anterior ascending 
