COCHLIODONTIDJE. 209 
Genus STREBLODUS, Agassiz. 
[Morris & Eoberts (ex Agassiz, MS.), Quart. Journ. Geol. Soc. 
vol. xviii. 1862, p. 101 1 2 .] 
Posterior dental plate much inrolled ; antero-lateral border cross¬ 
ing the supporting cartilage at right angles, thus giving the plate 
a truncated appearance in front; postero-lateral border inclined 
inwards and backwards, and forming an acute angle with the 
inner margin. Hinder portion of the coronal surface tumid, and 
separated more or less abruptly from the less elevated front portion; 
the latter area often marked by small ridges and grooves proceeding 
directly from the outer to the inner border. 
The dental plate just described is evidently homologous with the 
single posterior plate of Poeciloclus and Deltoptychins, and with the 
two separate posterior plates of Cochliodus . In at least two species 
(S. oblong us, and the so-called upper dental plate of Deltopty chius 
wachsmuthi) the separate series of small teeth immediately in 
advance of this large tooth is known. 
By St. John and Worthen the dental plates referred to Streblodus 
are considered to pertain in reality to the genera Cocliliodus, Delto- 
ptychius, and Chitonodus. In one case, indeed, plates of this charac¬ 
ter have been found in natural association with an undoubted jaw 
of Cochliodus 2 ; but there is yet no proof of their connection with 
the two last-named genera, and it thus seems advisable to retain 
Streblodus provisionally independent, awaiting further evidence of 
the true relationships of the dental fragments on which it has been 
founded. 
Streblodus oblongus (Portlock). 
1843. Cochliodus oblongus, L. Agassiz, Poiss. Foss. vol. iii. p. 174 (name 
only). 
1843. Cochliodus oblongus, J. E. Portlock, Eep. Geol. Londonderry, 
p. 466, pi. xiv. a. figs. 5, 10. 
1855. Cochliodus oblongus, F. M'Coy, British Palteoz. Foss. p. 623, 
pi. 3 h. fig. 19, pi. 3 i. fig. 28. 
1862. Streblodus oblongus, Morris & Eoberts, Quart. Journ. Geol. Soc. 
vol. xviii. p. 101 (name only). 
1 The name only is here mentioned and applied to the species previously 
figured and described by Portlock and M'Coy under the name of Cochliodus 
oblongus. The type species being thus already well-defined in 1862, the generic 
name may be regarded as dating from that year. 
2 Cochliodus latus, Leidy, supra, p. 208. 
P 
