46 
8ELACHII. 
tho homologous parts of the latter are misinterpreted, the apical 
edge being regarded as tho anterior coronal margin, and the pos- 
terior half of tho coronal face as a portion of the root. It must, 
however, bo admitted that at this point there is no very philoso- 
phical line of distinction between the teeth named Helodus and tho 
Petalodonts. 
Form. 4" Loc. Lower Carboniferous (Bone-bed in Lower Limestone 
Shales) : Bristol, England. 
P. 2652. Four teeth ; Bristol. One of those specimens is unsym- 
metrical, evidently having been laterally placed. 
Enniskillen Coll. 
P.1464. Three teeth; Bristol. Egerton Coll. 
Petalodus davisii, sp. nov. 
Type. Detached teeth ; British Museum. 
Teeth extremely elongated, very similar to those of P. recites, but 
somewhat smaller and even longer in proportion to their height ; 
coronal surface with numerous vertical wrinkles and a tendency 
towards crenulation of tho margin ; root considerably crimped. 
Form. Loc. Lower Carboniferous Limestone : Armagh, Ireland. 
P. 2656 a, P. 2656. Two type specimens and sixteen similar teeth. 
Enniskillen Coll. 
P. 1463. Similar imperfect tooth ; Armagh. Egerton Coll. 
A larger imperfect tooth (P. 5456) from the Upper Carboniferous 
Limestone of Bichmond, Yorkshire, seems to indicate a species allied 
to the foregoing ; and another fragmentary tooth (P. 2913, Ennis- 
killen Coll.), from tho Lower Carboniferous Limestone of Armagh, 
has been described by Davis (Trans. Boy. Dublin Soo. [2] vol. i. 
1883, p. 509, pi. Ixi. fig. 2) under the name of Chomatodus acutus. 
Petalodus alleghaniensis, Leidy. 
1866. Sicarius extinctus, .1. Leidy, Proc. Acad. Nat. Sci. Philad. vol. vii. 
p. 414. 
1866. Petalodus alleghaniensis, J. Leidy, Joum. Acad. Not. Sci. Philad. 
[2] vol. iii. p. 161, pi. xvi. figs. 4-6. [Specific name, extvmtus, 
withdrawn.] , 
1866. Petalodus destructor, J. S. Newberry & A. H. Worthen, Pal. 
Illinois, vol. ii. p. 36, pi. ii. figs. 1-3. 
1870. Petalodus destructor, 0. St. John, Proc. Amer. Phil, Soc, vol. xi. 
p. 433. 
