172 
SE LAC mi. 
1872. Helodussimplex, Hancock & Atthey, Nat. Hist. Trans. Northumb. 
& Durham, vol. iv. p. 422. 
1875. Helodus simplex , J. Ward, [Proc.] N. Staffs. Nat. Field-Club, 
p. 220. 
1875. Helodus simplex , W. J. Barkas, Monthly Bev. Dental Surgery, 
vol. iff. p. 101, tigs, xlv.-xlviii. 
1888. Helodus simplex, It. H. Traquair, Geol. Mag. [3] yol. v. p. 84. 
Type. Detached teeth ; British Museum (in part). 
Dental crown very variable in form, but much elevated and 
generally obtuse, attaining a maximum breadth of O'Olo. The 
species is still imperfectly known, and many of the specimens men¬ 
tioned below are only provisionally assigned to it. 
Form. Log. Coal Measures: Staffordshire, Shropshire, York¬ 
shire, and Northumberland ; South Wales ; Lanarkshire. ~ 
P. 488. Tooth figured by Agassiz, tom. cit. pi. xix. fig. 9 ; Silver- 
dale, Staffordshire. Egerton Coll. 
P. 2906-7. Two groups of naturally-associated imperfect teeth, 
with remains of cartilage ; Longton, Staffordshire. 
Enniskillen Coll. 
P. 2908. Fragment of trunk, with imperfect dorsal fin-spine ; 
w Longton. Enniskillen Coll. 
P. 2909. Six comparatively pointed teeth ; Longton. 
Enniskillen Coll. 
P. 5160. Ten teeth; Longton. Purchased, 1885. 
P. 2910. Four teeth; Fenton, Staffordshire. Enniskillen Coll. 
P. 5159. Two naturally-apposed series of four small teeth ; Fenton. 
Purchased , 1885. 
P. 1440. Two teeth; Fenton and Silverdale. Egerton Coll. 
21422, 21975. Five detached teeth; also six smaller teeth naturally 
arranged in two adjoining series, doubtfully assigned to this 
species ; Carluke, Lanarkshire. Purchased , 1847-8. 
P. 2905. Associated teeth; Carluke. Enniskillen Coll. 
P. 2283. Two teeth; Carluke. 
Presented by George Griffiths, Esq., 1882. 
