PETALODONTIDiE, 
59 
Polyrhizodus concavus (Trautschold). 
1874. Dactylodus concavus , H. Trautschold, Nouv. Mem. Soc. Imp. 
Nat. Moscou, yoI. xiii. p. 294, pi. xxviii. fig. 1. 
Type. Detached teeth. 
Teeth of the typical form of P. magnus , but with fewer, often 
undivided, “ rootlets.” 
Form. Sf Loc. Carboniferous Limestone : Mjatschkowa, Govern¬ 
ment of Moscow, Russia. 
P. 4487. Two complete, one broken tooth. Purchased , 1884. 
P. 5111. Three teeth. Purchased , 1886. 
P. 5490. Five specimens. Purchased, 1888. 
The Collection also comprises a broken tooth (P. 227 a) of un¬ 
certain species, from the Carboniferous Limestone of Oreton, Shrop¬ 
shire. Weaver Jones Coll. 
The following species have also been founded upon detached teeth, 
but, except of P. lobatus , there are no examples in the Collection. 
To this species is probably referable a broken tooth (P. 2979, 
Enniskillen Coll.) from the St. Louis Limestone, Monroe Co., 
Illinois, L.S.A. 
Polyrh izodus am/plus, St. John & TYorthen, Pal. Illinois, vol. vi. 
(1875), p. 387, pk xiii. fig. 13.—St. Louis Limestone; 
Illinois, Missouri. 
Polyrhizodus carbonarius, St. John & TV orthen, tom. cit. p. 389, 
pi. xa. figs. 24, 25, pi. xiii. fig. 10.—Coal-Measures; 
Illinois. 
Polyrhizodus ( Dactylodus ) concavus, St. John & Worthen (non 
Trautschold), tom. cit. p. 390, pi. xiii. figs, 17, 18.—St. 
Louis Limestone : Illinois. 
Polyrhizodus dentatus , Newberry & TYorthen, Pal. Illinois, vol. ii. 
(1866), p. 50, xfi. iii.fig. 10.—Chester Limestone ; Illinois, 
Polyrhizodus (. Dactylodus ) excavatus, St. John & TYorthen, tom. cit. 
p. 392, pi. xiii. fig. 16.—Chester Limestone ; Illinois. 
Polyrhizodus ( Dactylodus ) infiexus, Newberry & TV orthen, op. cit, 
vol. ii. p. 48, pi. iii. fig. 8.—Chester Limestone ; Illinois. 
Polyrhizodus littoni, Newberry & TYorthen, op. cit. vol. iv. (1870), 
v . p. 357, pi. iv. fig. 10.—St. Louis Limestone ; Missouri.^**' W.P/g 
Polyrhizodus (. Dactylodus ) lobatus, Newberry & TYorthen, op. cit . 
vol. ii. p. 47, pk iii. fig. 7; CtenoptycJiius cligitatus, J, Leidy, 
