252 
ACTINOPTEEYGII. 
middle point between the dorsal and ventral borders of the fish. 
11 vertical series of scales. 
The splenial dentition named Pycnodus achillis is characterized 
thus:—Teeth of principal series at least twice as broad as long, 
exceeding in width the two outer series and irregularly bordered 
within by one row of small round teeth ; those of the inner flanking 
series also at least twice as broad as long, sometimes subdivided; 
those of the outermost series small and round. 
Form. Sf Log. Cretaceous: Pietraroj a, Naples. 
Not represented in the Collection. 
Ccelodus costae, Heckel. 
1850. Pycnodus rhombus , 0. G. Costa ( em'ore ), Atti Accad. Pontan. 
vol. v. p. 352, pi. iv. fig. 8 (non pi. v. fig. 1). 
1856. Ccelodus costce, J. J. Heckel, Henkschr. k. Akad. Wiss., math.- 
naturw. Cl. vol. xi. p. 203. 
Type. Nearly complete fish. 
A small species attaining a length of about 0'105. Maximum 
depth of the trunk much exceeding one-half, and length of head 
with opercular apparatus equalling one-third of the total length of 
the fish. Teeth of principal (inner) series on splenial about three 
times as broad as long, indented on the apex and with crenulated 
margin. Dorsal fin with about 46 rays, occupying more than half 
of the back; anal fin with about 35 rays, arising more posteriorly. 
10-12 vertical series of scales. 
Form. Sf Log. Upper Jurassic: S. Italy. 
P. 1671 a. Small specimen displaying median fins and a few of the 
splenial teeth; Torre d’Orlando, near Naples. 
Egerton Coll. 
P. 4394. More imperfectly preserved fish, 0-105 in length, also 
showing some of the teeth; Torre d’Orlando. 
Ennislcillen Coll. 
Ccelodus mantelli (Agassiz). 
1827. “ Palates of an unknown fish,” G. A. Mantell, Foss. Tilgate 
Forest, p. 58, pi. xvii. figs. 26, 27. 
1833. Pycnodus microdon, L. Agassiz, Poiss. Foss. vol. ii. pt. i. p. 17. 
1839-44. Pycnodus mantellii, L. Agassiz, ibid. pt. ii. p. 196, pi. lxxii. a. 
figs. 6-14. 
1839-44. Gyrodus mantellii , L. Agassiz, ibid. pt. ii. p. 234, pi. lxix. a. 
fig. 18. [Splenial; British Museum.] 
