198 
OSTEOSTRi-CI. 
P. 5083. Three similar specimens. 
Presented by John Edward Lee, Esq., 1885. 
P. 5371. F our similar specimens, one showing traces of the large 
superficial tuberculations. Purchased, 1887. 
P. 6113 a. Similar specimen, showing traces of the large superficial 
tuberculations. Presented by George H. Piper, Esq., 1889. 
P. 5314, P. 6113. Two imperfect shields in mudstone, the second 
showing the transverse banding of the posterior plate. 
Presented by George H. Piper, Esq., 1887-89. 
Auchenaspis verrucosa (Eichwald);* 5 
1854. Thyestes verrucosus, E. von Eichwald, Bull. Soc. Imp. Nat. 
Moscou, pt. i. p. 108, pi. ii. fig. 1. 
1S56. Ceplialaspis verrucosus, C. H. Pander, Foss. Eische Silur. Syst. 
p. 47, pi. iv. figs. 1, 3-7. 
1858. Cephalaspis verrucosus, T. H. Huxley, Quart. Journ. Geol. Soc. 
vol. xiv. p. 269. 
1860. Thyestes verrucosus, E. von Eichwald, Leth. Rossica, vol. i. pt. ii. 
p. 1532. 
1866. Thyestes verrucosus, E. Schmidt, Verhandl. russ.-kais. mineral. 
Ges. St. Petersburg, [2] a t o1. i. p. 225, pi. iv. figs. 1-12. 
Type. Shield ; University of St. Petersburg. 
The type species of Thyestes. Shield resembling that of A. eger- 
toni in form and proportions ; external margin of anterior plate 
with a regular close series of blunt tuberculations ; transverse sulci 
between the components of the posterior plate prominent. Super¬ 
ficial ornament consisting of three symmetrically arranged, paired, 
longitudinal series of large tubercles, extending the whole length of 
the shield, with irregularly scattered small tubercles between; the 
longitudinal median ridge of the posterior plate apparently consist¬ 
ing of imperfectly-fused large tubercles. 
As remarked by Huxley and Schmidt, the supposed jaws de¬ 
scribed by Pander are fragments of the tuberculated rim cf the 
anterior shield. The orbits have not been indicated in published 
figures and descriptions, but they are as distinctly shown in some of 
the original specimens as in the typical Auchenaspis from Hereford¬ 
shire. The markings determined as orbits by Schmidt are too far 
forwards and too small, and the supposed median longitudinally- 
elongated vacuity is the now well-known large superficial fossa. 
Form. Loc. Upper Silurian : Isle of Oesel, Baltic Sea. 
Not represented in the Collection, 
