250 
BELACHII. 
P. 2122. Imperfect narrow tooth ; Jena. Egerton Coll. 
28476 a. Three imperfect elongated teeth, and one from a more 
anterior situation ; Cruilshcim, Wiirtemberg. 
Purchased, 1853. 
P. 2667. Abraded elongated tooth ; Crailshoim. Ennislcillen Coll. 
P. 2129. Two anterior teeth ; Wiirtemberg. Egerton Coll. 
Genus HYBODUS, Agassiz. 
[Poiss. Poss. vol. iii. 1837, p. 41.] 
Syn. Sphenmehus, L. Agassiz, tom. cit. 184.1, p. 201 (in part). 
(P) Meristvdon, L. Agassiz, tom. cit. 1843, p. 280. 
(?) Selachidea, F. A. Qiicnstedt, llandb. I'otrefakt. 1862, p. 17.3. 
Teeth conical or cuspidate, the crown more or le.ss striated, with 
one principal elevation, and one or more lateral prominences on eitlicr 
side diminishing outwards ; root much or moderately depressed. 
Symphysial teeth few, relatively large. Dorsal fin-spine.s longi- 
tudinally ridged and grooved, the ridges not denticulated ; two 
posterior longitudinal scries of denticles, not marginal, but placed 
together mesially. Anterior dorsal spine longer and more slender 
than the posterior. Shagreen sparse, consisting of small conical, 
radiately-grooved tubercles, sometimes fused into groups of three. 
Two largo hook-shaped, semi-barbed dermal spines immediately 
behind each orbit. Notochord persistent. 
It will be convenient to arrange the species of this genus in 
stratigraphical order, the detached teeth from some horizons being 
doubtfully i)laced here until the discovery of more satisfactory 
specimens. 
The dorsal fin-spines do not appear to afford constant specific 
characters, and all determinations attempted below must thus be 
regarded as provisional. 
Hybodus plicatilis, Agassiz. 
1837. Ilyhodus plicatilis, II. B. Geinitz (cz Agassiz, MS.), Beitr. Kennt. 
Thiiring. Muschelkalkgeb. p. 22, pi. iii. lig. 8. 
1843. Hybodus plicatilis, L. Agassiz, Poiss. Foss. vol. iii. p. 189, pi. xxn. «. 
fig. 1, pi. xxiv. ligs. 10, 13. 
(?) 1843. llybodiis lonyicmms, L. Agassiz, tom. cit. p. 191, pi. xxiv. figs. 
19-21, 23 (71011 fig. 22). 
1844. Hybodus plicatilis, U. von Meyer & T. Plieninger, Beitr. Pal. 
Wiirttembergs, p. Ill, pi. .xii. figs. 51, 70,71. 
1844. Hybodus lonyiconus, II. von Meyer & T. Plieninger, op. cit. p. 66; 
pi. xii. figs. 64, 6G. 
