196 
05TE0STRACI, 
banding of the posterior shield described as characteristic of Tliy- 
estes. That the two generic names pertain to a single type thus 
appears certain, and we prefer that of Auchenaspis as being most 
accurately and recognizably defined. 
Auchenaspis salteri, Egerton. 
1857. Auchenaspis salteri, Sir P. Egerton, Quart. Journ. Geol. Soc. 
Yol. xiii. p. 286, pi. ix. figs. 4, 5. 
1870. Auchenaspis salteri , E. R. Lankester, Fishes Old Red Sandst. 
pt. i. (Pal. Soc.), p. 56, pi. xiii. figs. 7, 8. 
Type. Imperfect shield ; British Museum. 
The type species, of very small size, the two shields having a 
maximum antero-posterior measurement of about 0*011. Orbits 
28 . 
Eig. 29. 
Fig. 28. Auchenaspis salteri, Egert.—Outline of shield, after Lankester. 
Fig. 29. Auchenaspis egertoni, Lank.—Outline of shield, after Lankester. 
placed in advance of the middle point of the anterior shield ; cornua 
not much produced and scarcely divergent; [ornament unknown]. 
Form. Loc. Upper Ludlow Tilestones : Ludlow. 
45952. Type specimen. Lightbody Bequest. 
P. 674. Internal impression of shield. Egerton Coll. 
Auchenaspis egertoni, Lankester. 
[Plate X. figs. 5, 6.] 
1870. Auchenaspis egertoni , E. R. Lankester, Fishes Old Red Sandst. 
pt. i. (Pal. Soc.), p. 57, pi. xiii. figs. 3-5. 
Type. Shields ; Oxford Museum. 
A species somewhat larger than the type, the two shields having 
a maximum antero-posterior measurement of about 0'02. Orbits 
situated in the middle of the anterior shield ; cornua divergent, 
produced to extend at least as far as the hinder margin of the pos- 
