0LIG0PLEURIDJ3. 
499 
spines in advance of the dorsal fin, and part of the rays 
apparently of the pectoral fin. The second specimen dis¬ 
plays the considerable expansion of the lamince of the 
neural and haemal arches, the acuminate anterior portion 
of the dorsal fin ’with fulcra on the first ray, and the 
rounded form of the scales. Lewis Coll. 
P. 5994. Imperfect head and anterior abdominal region with pec¬ 
toral fin, apparently of this fish ; Hakel. The head is 
too fragmentary for description and the vertebral centra 
are obscure. The pectoral fin-rays are broad, much 
divided and very closely articulated in the distal portion ; 
fulcra occur on the anterior margin of the fin, and there 
are traces of slender basal bones. Lewis Coll. 
It is still not possible to distinguish from Spathiurus the genus 
Opsigonus (D. G. Kramberger, in F. Bassani, Denkschr. k. Akad. 
Wiss., math.-naturw. Cl. vol. xlv. 1882, p. 200), from the Cretaceous 
of the Island of Lesina, Dalmatia. It is not determined, however, 
whether this fish had a rounded or forked tail, whether fulcra are 
present or absent on any fin except the caudal, and whether or not 
there is a series of free neural spines in the abdominal region. 
The single known species is Opsigonus megaluriformis (Kramberger, 
loc. cit. p. 200, and Bad. Jugoslav. Akad. vol. lxxii. 1885, p. 14, 
pi. iv. fig. 1, and Soc. Hist.-Kat. Croatica, vol. i. 1886, p. 125), the 
type specimen being preserved in the Geological Museum of the 
University of Agram. The name of Opsigonus gracilis is given by 
J. V. Bohon (Mem. Acad. Imp. Sci. St. Petersbourg, [7] vol. xxxviii. 
no. 1, 1890, p. 11, pi. i. fig. 6) to a small Palaeoniscid fish from the 
Jurassic of Ust-Balei, Government of Irkutsk, Siberia, now in the 
Museum of the Imperial Academy of Sciences, St. Petersburg. 
The following specimens probably represent a member of the 
family Oligopleuridse, but are too imperfect for precise determina¬ 
tion :— 
P. 7584. Fragment of trunk and fin labelled u Calamoporus 
cylindricus , Agass.,” by Agassiz, evidently intended for 
Calamopleurus cylinclricus , L. Agassiz, Edinb. Kew Phil. 
Journ. vol. xxx. (1841), p. 84, and Comptes Bendus, 
vol. xviii. (1844), p. 1012 ; Cretaceous, Province of Ceara, 
Brazil. The scales are cycloidal, very much imbricating 
and apparently longer than deep; the fin-rays are widely 
spaced and much divided distally. History unlcnown. 
