CESTBACI0NTID2E. 
247 
a short acute central crest, from which a few sharp 
simple ridges diverge; Mjatschkowa. These are very 
similar to P. acutus, Newberry & Worthen 1 . 
Purchased , 1884. 
P. 5117. A similar, but more nearly perfect specimen; Mjatschkowa. 
Purchased , 1886. 
The following “ species ” of Petrodus are not represented in the 
Collection :—P. coronatus, H. Trautschold, Nouv. Mem. Soc. Imp. 
IN at. Moscou, vol. xiv. (1879), p. 60, pi. vii. fig. 14 ( Ostinaspis ), from 
the Carboniferous Limestone of Mjatschkowa, near Moscow ; P. (?) 
pustulosus , Newberry & Worthen, Pal. Illinois, vol. iv. (1870), p. 369, 
pl. ii- fig* 5, pi. iii. fig. 6, from the Burlington Limestone of Iowa ; 
P. ryckolti , L. G. de Koninck, Eaune Calc. Carbf. Belg. pt. i. (1878), 
p. 37, pl. v. fig. 12, from the Lower Carboniferous Limestone of 
Tournai, Belgium; and P. simplicissimus , H. Trautschold, Nouv. 
Mem. Soc. Imp. Nat. Moscou, vol. xiii. (1874), pl. xxviii. fig. 12, g-i 
( Ostinaspis ), from the Carboniferous Limestone of Mjatschkowa. 
The tubercles named Stemmatodus 2 are small clusters of sharp 
denticles. They occur in the English Coal-Measures, and are repre¬ 
sented in the Collection by four specimens (Nos. 35000-1. Pur¬ 
chased, I860) from Teuton, North Staffordshire. Eroni the American 
Lower Carboniferous the following u species ” are distinguished :— 
S. cheiriformis, St. John & Worthen, Pal. Illinois, vol. vi. (1875), 
p. 330, pl. viii. fig. 30, from the Burlington Limestone of Iowa ; 
8. bicristatus, St. John & Worthen, tom. til. p. 331, pl. viii. figs. 32, 
33, 35, from Iowa; 8. bifurcatus , St. John & Worthen, tom. cit. 
p. 330, pl. viii. fig. 31, from Iowa; 8. compactus, St. John & 
Worthen, tom. tit. p. 334, pl. viii. fig. 38, from the Chester Lime¬ 
stone, Illinois ; 8. Tceokuk , St.John & Worthen, tom. tit. p. 334, from 
the Keokuk Limestone, Illinois and Iowa; 8. simplex , St. John & 
Y orthen, tom. tit. p. 332, pl. viii. figs. 36, 37, from Iowa; and 
8. symmetries, St. John & Worthen, tom. cit. p. 333, pl. viii. fig. 28, 
from Iowa. 
To 8tyracodus is referred one species, 8. acutus , Giebel, sp. (Germar, 
Yerstein. Steinkohlengeb. Wettin, 1849, p. 70, pl. xxix. fig. 3), from 
the Coal-Measures of Wettin, Prussia. It had previously been 
described as Centrodus acutus, Giebel (Eauna Yorwelt, Eische, 181$, fif 
1 Pal. Illinois, vol. ii. (1866), p. 72, pl. iv. fig. 17; (?) Ostinaspis acuta , 
H. Trautschold, Nouv. Mem. Soc. Imp. Nat. Moscou, vol. xiii. (1874), p. 299, 
pl. xxviii. fig. 12, e, f. 
2 This name is preoccupied, having been employed by Heckel for a Jurassic 
Pycnodont (Denksckr. math.-naturw. Cl. k. Akad. Wiss. Wien, vol. xi. 1856, 
p. 202). 
