﻿198 OSTEOSTRACI. 



P. 5083. Three similar specimens. 



Presented by John Edward Lee, Esq., 18S5. 



P. 5371. Pour 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). 



1854. Thyestes verrucosus, E. von Eichwald, Bull. Soc. Imp. Nat. 



Moscou, pt. i. p. 108, pi. ii. fig. 1. 

 1856. Cephalaspis verrucosus, C. H. Pander, Foss. Fische 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, F. Schmidt, Verhandl. russ.-kais. mineral. 



Ges. St. Petersburg, [2] vol. 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. <y Loc. Upper Silurian : Isle of Oesel, Baltic Sea. 



Not represented in the Collection. 



