288 
ARTHRODIRA. 
P. 685. Ten specimens exhibiting plates of the head and trunk. 
Egerton Coll. 
49185-86. Two specimens of the head and armoured trunk, in 
counterpart. Broad teeth are shown in the mandible of 
both specimens. Purchased, 1876. 
21574, a, b. Three examples of the dermal plates of the head and 
trunk, the second and third being preserved in counter¬ 
part. In the first specimen the median occipital of the 
cranial shield exhibits the characteristic median elevation, 
and the “posterior ethmoidal” (pineal) shows a distinct 
cast of the large central pit on its inferior aspect. 
Presented by Norman McLeod, Esq., 1847. 
20792 a-b. Fine example of the dermal plates of the head and 
trunk, preserved in counterpart. The maxillary or sub¬ 
orbital elements are displaced, and the supposed operculum 
is observed immediately behind on each side. The tuber¬ 
cular ornament is very coarse ; and behind the median 
dorsal plate there occurs one of the pelvic basipterygia. 
Presented by Col. Sir Proby T. Cautley, K.C.B., 
and — Gordon, Esq., 1847. 
F. 5960-1. Two specimens showing various dermal plates, the first 
including the mandibular rami with teeth. 
Purchased, 1889. 
P. 685 c. Median dorsal plate, broken to exhibit the extent of the 
inner longitudinal keel. Egerton Coll. 
P. 5060. Median dorsal plate. Presented by J. E. Lee, Esq., 1885. 
P. 6073. Median dorsal plate with imperfect portions of other 
elements. Presented by F. Harford, Esq., 1889. 
P. 3225. Crushed median dorsal plate. Ennislcillen Coll. 
(vi.) Tynet Burn. 
43617. Imperfect individual wanting the posterior half of the 
caudal region, lateral aspect, in counterpart. The dermal 
plates of the head and trunk are much broken, but several 
characteristic elements are exhibited; while the region 
immediately behind the armour is especially well preserved. 
The latter is shown, of the natural size, in PL VII. fig. 2, 
and the parts are lettered in accordance with the following 
description. Emerging from beneath the median dorsal 
