PYCXODONTID 2E. 
189 
in the more arched form of the back, deeper trunk, and the 
remarkable development of the pectoral, dorsal, and anal fins. 
Form. Sf Loc. Lower Kimmeridgian (Lithographic Stone) : Ba¬ 
varia. 
Not represented in the Collection. 
A fish from the Lithographic Stone of Cirin, Ain, Prance, much 
resembling the two preceding species, is named N. margaritce , 
Thiolliere (Bull. Soc. Geol. Prance, [2] vol. xv. 1858, p. 783), and 
figured without description in Thiolliere, Poiss. Poss. Bugey, pt. ii. 
(1873), pi. vi. fig. 4. ~/oy^Ajj 
Either to the Macrosemiidae or to the Semionotidte may also per¬ 
haps be referred the problematical Triassic genus Orthurus (R. Kner, 
Sitzungsb. k. Akad. Wiss., math.-naturw. Cl. vol. liii. 1866, p. 163). 
The trunk is comparatively elongated and is almost or quite scale¬ 
less on the flanks. A few of the inner teeth are enlarged and 
tritoral. There is little or no ossification in the notochordal sheath, 
anc 1 the ribs are extremely delicate. The pectoral fins are large 
and the pelvic fins remote ; the dorsal fin has an extended base-line 
but is not acuminate, and the anal is relatively very small; the 
caudal fin is truncated, not forked, A few undivided and unarti¬ 
culated rays occur at the origin of the dorsal and caudal fins, but 
ordinary fulcra are absent. All the fin-rays are delicate, and those 
of the dorsal and anal fins, though articulated, are not branched 
more than once. An elongated large scale occurs in front of the 
anal fin. The type species, 0. sturi (Kner, loc. cit. p. 163, pi. ii. 
fig- 1), is founded on a unique specimen from the Keuper of Raibl, 
Carinthia, in the Museum of the Austrian Geological Survey, 
Vienna. Another form from the “ Hauptdolom.it ” of Lumezzane, 
Lombardy, is also described by W. Deecke, Palseontogr. vol. xxxv. 
(1889), p. 136, pi. vii. fig. 9. 
Pamily PYCNODONTIDyE. 
Trunk deeply fusiform or cycloidal. Cranial bones robust, and 
a median occipital plate separating the parietal elements; facial 
bones delicate or wanting; opercular apparatus reduced to a small 
operculum, large preoperculum, and not more than two branchio- 
stegal rays ; mandibular suspensorium much inclined forwards and 
gape of mouth small; teeth prehen silo on the premaxilla and dentary, 
wanting on the maxilla (if this bone be present) and the pterygo¬ 
palatine arcade, tritoral on the single vomer and the splenials ; all 
