/2ls/{ no-'fi0footeJiev , 7 G/Z-t7cc+&/- 'ScS- P/SP?./^. 6~& - 
' 126 
ICHTHYODOmXLTTES- ^ „ . - 
't/o, y Genus PSAMMOSTEUS, Agassiz. 
[Poiss. Foss. y. G. R. 1845, p. 103.] 
Syn. Placosteus, L. Agassiz, Poiss. Foss. vol. i. 1844, p. xxxiii (name 
only). 
Psammolepis, L. Agassiz, ibid. p. xxxiv (name only). 
Spines and dermal plates of moderate size, the former much 
laterally compressed, usually unsymmetrical, broad and triangular, 
with a laige internal cavity and short base of insertion. External 
surface ornamented with numerous, closely arranged, rounded or 
elongated, tubercles of gano-dentine, usually stellate and rarely 
arranged in regular series. 
As pointed out by Agassiz and Pander, the histological structure 
of these ichthyodorulites is suggestive of that of Selachian dermal 
armour; and in external characters they are most nearly paralleled 
by Or acanthus, as described below. $. fd~ 3 sp y ft 3^ S.fr 
/ v*- ^ /?6 / /■ 
/ 1 Psammosteus mssandrlnus^ Agassiz. 
1844. Placosteus mceandrinus , L. Agassiz, Poiss. Foss. vol. i. p. xxxiii 
(name only). 
1845. Psammosteus mceandrinus, L. Agassiz, Poiss. Foss. V. G. E. 
p. 104, pi. xxvii. figs. 5, 6. 
!845. Ctenacanthus serrulatus,L. Agassiz, ibid. p. 119, pi. xxxiii. fig. 24. 
1857. Asterolepis P, C. H. Pander, Placoderm. devon. Syst. p. 20, pi. vii. 
figs. 16-18. 
lb-5b. Psammosteus mceandrinus , G. Kade, Programm k. Eealschule zu 
Meseritz, p. 11, figs. 2-5. 
1860. Psammosteus mceandrinus, E. von Eichwald, Leth. Eossica, vol. i. 
p. 1516. 
. 1880, Coccosteus megalopteryx , H. Trautschold (errore), Verhandl. russ 
k. mineral. Gesell. St. Petersburg, p. 152, pi. vi. fig. 1, pi. vii. fig. 2. 
1889. Coccosteus megalopteryx, H. Trautschold {errore), Zeitschr. 
deutsch. geol. Gesell. vol. xli. p. 36. 
Ib90. “ Selachian appendages,” R. H. Traquair, Ann. Mag. Nat. Hist 
[6] vol. v. p. 134. 
^ ** »r 6“rt\ ° 
Type. Unknown. 
The type species. 0 p*~*J*>- y 
Form. 6f Loc. Devonian : N.W. Russia. 
7 6 urt\ c-Uf r\ 
P. 4493. Two spines, imperfect distally, of the form assigned to 
this species by Eichwald, but described as Coccosteus 
megalopteryx by Trautschold ; from banks of River Ssjass. 
In one specimen there are indications of a narrow inserted 
portion at the base of one side and a much deeper insertion 
