40 
SELACHII. 
Genus FISSODUS, St. John & Worthen. 
[Pal. Illinois, vol. vi. 1875, p. 413.] 
Teeth very similar to those of Janctssa and Petalorhynchus , but 
distinguished by the coronal margin being deeply cleft or divided 
into two or three broad, acuminate points. 
Fissodus bifidus , St. John & Worthen, tom. cit. p. 414, pi. xiii. 
figs. 1, 2.—Chester Limestone ; Illinois. 
Fissodus pattoni, It. Etheridge, jun., Geol. Mag. [2] vol. iv. (1877), 
p. 306, pi. xiii. figs. 2, 3.—Lower Carboniferous Lime¬ 
stone ; S. Scotland. 
Fissodus tricuspnclatus , St. John & Worthen, tom. cit. p. 415, pi. xiii. 
fig. 3.—Chester Limestone ; Illinois. 
The genus Cholodus , St. John & Worthen, tom. cit. p. 415, is 
founded upon imperfect teeth from the Upper Coal-Measures of 
Illinois and Iowa, resembling those of Fissodus very closely. The 
only' described species is C. incequalis , St. John & Worthen, tom. cit. 
p. 416, pi. xiii. figs. 4, 5. ^ 
Genus PETALORHYNCHUS, Newberry & Worthen (ex 
Agass. MS.). 
[Pal. Illinois, vol. ii. 1866, p. 32.] 
Teeth with crown compressed, thin, concavo-convex, petal-shaped, 
relatively high and narrow : basal imbricating folds few. The root 
is long, tapering, and undivided. The complete dentition consists 
of three or more parallel antero-posterior series, the crowns of the 
teeth in the median row being very high and narrow compared with 
those on either side. 
Petalorhynchus psittacinus (McCoy). 
1843. Petalodus psittacinus, L. Agassiz, Poiss. Foss. vol. iii. pp. 174, 
384 (name only). 
1843. Petalodus sagittal us, L. Agassiz, tom. cit. pp. 174,384 (name only). 
1855. Petalodus psittacinus, F. McCoy, Brit. Palaeoz. Foss. p. 636, pi. 3i. 
^ fig- 4- 
1855. Petalodus sagittatus, F. McCoy, op. cit. p. 636, pi. 3i. figs. 2, 3. 
1862. Petalorhynchus psittacinus , Morris & Roberts, Quart. Journ. Geol. 
Soc. vol. xviii. p. 101 (name only). 
1881. Petalorhynchus psittacinus , J. W. Davis, Rep. Brit. Assoc, p. 646. 
