PSAMMODONTIDiE, 
107 
Psammodus specular is, Trautschold. 
1874. Psammodus speculates, H. Trautschold, Nouv. Mem. Soc. Imp. 
Nat. Moscou, yol. xiii. p. 288, pi. xxviii. fig. 4. 
Type. Detached tooth. 
The coronal surface of the fossil teeth is smooth, though, as these 
are all more or less abraded, it may have originally been rugose. 
The inner teeth are about two and a half times as broad as long, 
and somewhat twisted round the long axis. The crown is nearly 
twice as thick as the root, and is not downwardly bent at either 
extremity. 
As already remarked by Trautschold, it is not improbable that 
these teeth may be truly referable to P. angustus , being perhaps 
the opposing teeth to those described under the last-named species. 
The distinctness of their shape, however, renders it convenient to 
separate them until further evidence as to their relationships is 
discovered. 
Form. Sf Log. Lower Carboniferous Limestone: Mjatschkowa, 
Government of Moscow, Russia. 
P. 4488. Lour teeth and one detached crown. Purchased , 1884. 
P. 5113. Two detached dental crowns, of large size. 
Purchased , 1886. 
The following species have also been founded upon detached 
teeth, but there are no examples in the Collection :— 
Psammodus angularis , Newberry and Worthen, Pal. Illinois, 
vol. ii. (1866), p. 107, pi. xi. fig. 2. (?) “ P. porosus 
Agassiz,’ 7 ibid. p. 107, pi. xi. fig. 1; P. angularis , St. 
John & Worthen, Pal. Illinois, vol. vii. (1883), p. 222, 
pi. xix. figs. 1, 2.—Chester Limestone; Illinois. 
Psammodus ccelatus, St. John & Worthen, op. cit. vol. vii. (1883), 
p.- 217, pi. xviii. fig. 1.—St. Louis Limestone ; Iowa. 
Psammodus crassidens , St. John & Worthen, op. cit. vol. vii. (1883), 
p. 218, pi. xviii. figs. 2-6; P. rugosus, Newberry & 
Worthen ( non Agassiz), op. cit. vol. ii. p. 108, pi. xi. 
fig. 3.—St. Louis Limestone; Illinois, Iowa. 
Psammodus glyptus, St. John & Worthen, tom. cit. p. 209, pi. xiv. 
figs. 5, 6.—Upper Burlington Limestone; Illinois. 
Psammodus grandis , St. John & Worthen, tom. cit. p. 211, pi. xv. 
figs. 1-3.—Keokuk Limestone ; Iowa. 
Psammodus inflexus, H. Trautschold, Nouv. Mem. Soc. Imp. Nat. 
