CEPHALASPIDiE. 27 



Characters. — Scutum ovale : discus centralis convexus postice truncatus et spina 

 brevissima, striis longitudinalibus minutis externe ornatus : rostrum breve, rotundatum, 

 striis transversis ornatum : cornua cum disco usque ad truncationem juncta, externe striis 

 longitudinalibus ornata. 



Stratigrapldcal Position. — This fossil has at present been found only in the Downton 

 Sandstone. 



History. — ^Mr. Salter, in conjunction with Prof. Huxley, described this species as 

 Pteraspis Banksii, from specimens found by Mr. Banks at Kington in 1859. 



General Remarks. — There is little to be said of this species beyond what has been said 

 in the description of the genus. The rostrum projects a little beyond the rest of the 

 scute, and is rounded off in a gentle curve ; the lateral cornua embrace the central oblong 

 convex disc throughout its length, terminating abruptly with it in the posterior region, 

 which has the aspect of being sharply truncated. A little above the truncation of the 

 scute in the median line is the origin of a short spine or projection. I have seen nothing 

 in the specimens I have examined of the " costuli" and double series of ten " tubercles" 

 mentioned in Messrs. Huxley and Salter's description, which I cannot but think is 

 erroneous in this respect. On either side of the rostrum in casts is a marginal tubercle, 

 probably connected with the orbit, but specimens sufficiently well preserved to make this 

 clear have not been found. The surface is very finely striated, and the convexity of 

 the central portion of the shield in uncrushed examples very great. The length of the 

 scute of this species is from an inch and a half to an inch and three quarters ; its breadth 

 from a little over an inch to an inch and a half. 

 Locality. — Kington, Herefordshire, 



2. Cyathaspis (?) Symondsi, Lankester. PI. VI, fig. 5. 



Cyathaspis (?) Symondsi, Lankester. Brit. Assoc. Rep., Trans. Sect., p. 58, 1864. 



It is useless to give any definite character to this species at present, as it rests on a 

 single specimen, which, though indicating a remarkable Fish belonging apparently to 

 this genus, is too imperfect to warrant any further affirmation in regard to it. 



This specimen has been for some time in the Collection of the Geological Survey, 

 and is labelled as coming from the Cornstones, Herefordshire ; it is a well-pre- 

 served smooth-surfaced cast of the interior of the scute, and measures three inches 

 and a half in length, and two and a half in breadth, being one of the largest He- 

 terostraci known. Its form is rather rectangular than ovoid. The central and median 

 portion is convex and raised up above the rest of the scute ; it projects backwards, some 

 little way from the flatter portion, and has a rounded truncated posterior margin. In 

 front the flat portion is produced into a small rostrum which has an incurved frontal 



