CESTEACIONIIDiE. 
247 
a short acute central crest, from which a few sharp 
simple ridges diverge ; Mjatschkowa. These are very 
similar to P. acutus, Newberry & Worthen'. 
Purchased, 1884, 
P. 5117. A similar, hut 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. 
Nat. Moscou, vol. xiv. (1879), p. 60, pi. vii. fig. 14 {Ostinaspis), from 
the Carboniferous Limestone of Mjatschkowa, near Moscow ; P. (?) 
pustalosus, Newberry & IVorthcn, Pal. Illinois, vol. iv. (1870), p. 309, 
pi. ii. fig. h, pi. iii. fig. 0, from the Purlingtou Limestone of Iowa ; 
P. rycholti, L. G. de Koninck, Faunc Calc. Curbf. Belg. pt. i. (1878), 
p. 37, pi. V. fig. 12, from the Lower Carboniferous Limestone of 
Tournai, Belgium; and P. simplicissimus, H. Trautschold, Nouv. 
Me'ni. Soc. Imp. Nat. Moscou, vol. xiii. (1874), pi. xxviii. fig. 12, g-i 
(Ostinasjns), from the Carboniferous Limestone of Mjatschkowa. 
The tubercles named Stemmalodus^ are small clusters of sharp 
denticles. They occur in the English Coal-Measures, and are repre- 
sented in the Collection by four specimens (Nos. 3500(1-1. Pur- 
chased, 1 860) from Fenton, North Btaftbrdshire. From the -Imerican 
Lower Carboniferous the following “ species ” are distinguished : — 
S. cheiriformis, St. John & 'Worthen, Pal. Illinois, vol. vi. (1875), 
p. 330, pi. viii. fig. 30, from the Burlington Limestone of Iowa ; 
S. bicrisUiim, St. John & Worthen, tom. cil. p. 331, pi. viii. figs. 32, 
33, 35, from Iowa ; S. hifurcatus, St. John & Worthen, tom, eit. 
p. 330, pi. viii. fig. 31, from Iowa; S. compacitis, St. John & 
Worthen, torn. eit. p. 334, pi. viii. fig. 38, from the Chester Lime- 
stone, Illinois; <S'. St. John & Worthen, tom.cit. p. .334, from 
the Keokuk Limestone, Illinois and Iowa; /S', simple.v, St. John & 
Worthen, tom.cit. p. 332, pi. viii. figs. 36, 37, from Iowa; and 
S. sgmmetricus, St. John ife Worthen, tom. cit. p.333, pi. viii. fig. 28, 
from Iowa. 
To Slgraeodus is referred one species, S. acutus, Giebel, sp. (Germar, 
Verstein. Steinkohlengeb. Wettin, 1849, p. 70, pi. xxix. fig. 3), from 
the Coal-Measures of Wettin, Prussia. It had previously been 
described as Centrodus acutus, Giebel (Fauna Vorwclt, Fische, 1847, 
» Pal. IllinoiB, Tol. ii. (18GC), p. 72, pi. iv. fig. 17 ; (?) Ostinaspis acuta. 
H. Trautschold, Kouv. Mum. Soc. Imp. Nat. Moscou, vol. xiii. (1874), p. 299, 
pi. xxviii. fig. 12, e, /. 
2 This name is preoccupied, having been employed by Ileokel for a Jurassic 
Pycnodont (Denksuhr. math.-naturw. Cl. k. Akad. Wiss. Wien, vol. xi. 1856, 
p. 202). 
