106 
SELACHII. 
tooth are approximately equal, the latter measurement sometimes 
slightly exceeding the former. 
The third of the specimens mentioned below is intermediate 
between the types of H. trapeziformis and II. quadratus, which it 
seems inadvisable to separate specifically. All are from the 
Enniskillen Collection. 
Form. S)' Loo. Lower Carboniferous Limestone : Armagh, 
p. 2599. Type of Homalodus trapeziformis , Davis. 
P. 2600. Type of H. quadratus, Davis. 
P. 5323. Tooth intermediate between the foregoing. 
P. 5324. Smaller tooth, probably referable to the same species. 
Fsammodias Eomanowsky. 
1864. Psammodus angustus, H. Eomanowsky, Bull. Soc. Imp. Nat. 
Moscou, pt. ii. p. 159, pi. iii. fig. 6. 
1874. Psammodus angustus, H. Trautschold, Nouv. Mem. Soc. Imp. 
Nat. Moscou, vol. xiii. p. 289, pi. xxviii. fig. 5. 
1878. Psammodus angustus, L. G. de Koninck, Eaune Calc. Carb. 
Belg. pt. i. p. 45, pi. v. fig. 6. 
Type. Detached tooth. 
The coronal surface of unworn and un abraded teeth is probably 
rusose, though the majority of the fossils only show such markings 
upon the sides. The inner teeth are mostly about two and a half 
times as broad as long, the crown exhibiting a tumid rising towards 
its outer lateral extremity, where it is produced into a downwardly- 
directed plate extending over the root. The root is scarcely as 
thick as the crown, and likewise bent downwards at the lateral 
extremity. 
Trautschold mentions the occurrence of small square teeth of 
Psammodus in the same bed as the remains of the present species ; 
and these may probably be regarded as lateral teeth, like those of 
P. rugosus. 
Form. A Log. Lower Carboniferous Limestone : Alexine, Govern¬ 
ment of Toula, and Mjatschkowa, Government of Moscow, Eussia ; 
Eeluy, Belgium. 
P. 4485. Eive detached dental crowns and one complete tooth: 
Mjatschkowa. Purchased, 1884. 
P. 5112. Two detached dental crowns and one almost complete 
tooth; Mjatschkowa, Purchased, 1886. 
