48 
ACTINOPTEKYGII. 
Munich, the writer is now inclined to withdraw his comparison of 
this fossil with the supposed rostrum of those fishes (see supra, 
Pt. II. p. 395). 
Form. Sf Loc. Senonian : Kent. 
33221-24. Type specimen, being a portion of the tail described and 
figured, loc. cit.; Upper Chalk, Gravesend. The largest 
caudal fulcral scale measures 0-024 in maximum breadth, 
and 0*027 from the apex to the bifurcation of the base. 
Taylor Coll. 
Division B .—Baseosts rudimentary or absent in pelvic fins; 
dermal rays of dorsal and anal fins equal in number to 
the endoskeletal supporting elements; tail never hetero- 
cercal, usually abbreviate-heterocercal or homocercal\ 
rarely diphycercal. 
Suborder II. PROTOSPONDYLL 
Notochord persistent, or if more or less replaced by vertebrae, 
the pleurocentra and hypocentra in part of the caudal region re¬ 
maining distinct and alternating even when fully developed; tail 
abbreviate-heterocercal. Mandible complex, with well-developed 
splenial rising into a coronoid process, which is completed by a 
distinct coronoid bone. Infraclavicular plates wanting in the 
pectoral arch ; pectoral fin with more than five basals. Scales 
ganoid. In the living forms—air-bladder connected with the 
oesophagus in the adult, optic nerves not decussating, but forming a 
chiasma, and intestine with a spiral valve. 
Synopsis of Families. 
I. Mandibular suspensorium vertical or in¬ 
clined forwards and gape of mouth 
small. 
Trunk more or less deeply fusiform; 
vertebrae not more than rings ; teeth 
styliform or tritoral; fulcra large, 
and dorsal fin not extending more 
than half the length of the trunk . . Semionotidje (p. 49). 
Trunk elongate or elongate-fusiform; 
vertebrae not more than rings; teeth 
styliform; fulcra variable, and dorsal 
fin extending at least half the length 
of the trunk. Macrosemiid^ (p. 163). 
