424 
ACTIjSTOPTEKYGII. 
The type species, probably attaining a length of about 0*3. 
Length of head with opercular apparatus somewhat exceeding two 
thirds the maximum depth of the trunk, which nearly equals the 
length from the pectoral arch to the base of the caudal fin. Dorsal 
fin with 6 short and stout spines, which are nearly smooth; anal 
fin arising much nearer to the pectorals than to the caudal. 
External head-bones and scales very feebly rugose, the latter some¬ 
times quite smooth; nearly 30 scales in each transverse series in 
the abdominal region. 
Form. <^' Log. Senonian and Turonian : Sussex and Kent. 
25881. Eine small specimen, about 0*15 in length, showing the 
head, the origin of the dorsal and anal fins, traces of 
the pectoral and caudal fins, some caudal vertebrae and 
scales ; Chalk, Sussex. Dixon Coll. 
P. 6465. Larger imperfect fish; probably from Sussex. The 
characteristic head is shown, and there are indications of 
30 vertebrae, of which at least 12 are abdominal. The 
pectoral fin is proved to have been very small, with from 
10 to 12 rays; and there are three delicate anal fin- 
supports as far back as the 7th and 8th vertebrae from the 
end of the tail. Deckles Coll. 
4037, 4305. Eragmentary head and trunk, and a small piece of 
squamation ; Chalk, Lewes. An ossified sclerotic and 
some rays of the dorsal fin are exhibited. Mantell Coll. 
P. 3931, P. 4294. Eragment of small, and fragment of large head 
and trunk ; Chalk, Sussex. Enniskillen Coll. 
37751. Large head with abdominal region much fractured, but 
displaying some of the flank-scales ; Chalk, near Maid¬ 
stone. Purchased, 1863. 
49053. Eemains of opercular apparatus and trunk, showing ver¬ 
tebrae, clavicle, anterior part of dorsal fin, and smooth 
squamation; Chalk, Kent. Mrs. Smith’s Coll. 
P. 1951. Two fragmentary specimens, one showing the top of the 
cranium ; Chalk, Kent. Egerton Coll. 
P. 5683. Eemains of head and abdominal region, displaying scapu¬ 
lar arch and part of squamation; Lower Chalk, Durham, 
Harford Coll. 
