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BLOCHIID^. 
Genus BLOCHIUS, Volta. 
[Ittiolit. Veronese, 1796, p. liii.] 
Eostrum very slender, projecting far in advance of the mandible^ 
which articulates beneath the hinder end of the cranium ; rami of 
mandible probably fused at symphysis; teeth minute or absent. 
Vertebrae about 12 in the abdominal, 12 in the caudal region; the 
centra much elongated and constricted,imperfectly ossified. Pectoral 
fins small; [pelvic pair supposed to be present, but, if so, relatively 
small and jugular]; caudal fin slightly forked. Bony scutes 
diamond-shaped, slightly overlapping, completely and regularly 
covering the trunk and partly extending over the opercular appa¬ 
ratus and cheeks; two longitudinal series of scutes somewhat 
enlarged on each flank. 
So far as can be determined from the fractured specimens in the- 
Collection, the remarkably elongated rostrum of this genus bears 
much resemblance to the supposed dermal spines from the Upper 
Eocene named Coeloi'hynclms (see Part II. p. 120). When suflci- 
ently well-preserved rostra of the typical Blocliiiis are available for 
microscopical examination, it will be interesting to compare the 
structure with that of Coelorhynchus, and also with that of the 
apparently Chimseroid spines from the Cretaceous which commonly 
bear the same name. 
Blochius longirostris^ Volta. 
[Text-figure 22.] 
1796, Blochius longirostrisy G. S. Volta, Ittiolit. Veronese,, p. liii. 
pis. xii., Ixx. 
1843-44. Blochius longirosti'is, L. Agassiz, Poiss. Foss. vol. ii. pt. ii. 
p. 255, pi. xliv. 
1887. Blochius macroj^tei'us, A. de Zigno, Mem. E. Istit. Veneto, vol, 
xxiii. p. 25, fig. 7. [Imperfect fish with incomplete rostrum ; Zigno 
Coll., University of Padua.] 
Type. Imperfect fish; Paris Museum of Natural History. 
The type species, attaining a length of about a metre. Length of 
head with opercular apparatus about equal to that of the vertebral 
column; maximum depth of trunk contained about nine times in 
the same measurement. Dorsal fin-spines about 50 in number, 
the length of the longest apparently not exceeding the maximum 
depth of trunk; anal fin with about 25 rays, arising slightly nearer 
to the caudal fin than to the pectoral pair. Dermal scutes very 
PAKT IV. 2 Q 
