ASAPHUS. 153 



prominent, much wider apart than in the last species, the width from eye to eye being 

 greater than the whole length of the head. The eye is broad, and almost as high as broad, 

 and much curved, sunk in a depression of the cheek, and placed hardly its own breadth 

 from the marginal furrow (see fig. 2). Facial suture beneath the eye reaching very 

 little outwards, and cutting the margin beneath the outer edge of the eye. In front 

 it cuts the margin more abruptly than in A. tyrannm. 



The thorax is generally convex, but the axis is not very strongly separated from the 

 sides, but more so than in the allied species; and is somewhat narrower than the pleurae, 

 which curve down steeply from the fulcrum, placed at about one third out, and they 

 bend more sharply backward than in A. tyrannus -. their ends are more oblique and less 

 square, and the pleural groove is longer, much narrower, and somewhat deeper than in 

 that species. 



The tail is half-oval, rounded, not at all truncate at the end, and with a flat rim all 

 round, not concave as in the last. The axis narrow, more convex, shorter, and more 

 regularly tapering, and with fewer (fourteen or fifteen) rings. The sides are convex, 

 forming a channel against the flat margin, and with nine or ten ribs only (rarely eleven), 

 and these are longer, more curved, and more prominent than in A. tyrannus. The caudal 

 fascia has more closely set lines. 



The sculpture, too, is diff'erent. The same in character, it is much less prominent 

 and conspicuous. This may be due to the less size of the specimens, but there is a 

 difference in the only part where I can find it conspicuous, viz., the border of the tail, 

 where it is much closer, more thread-like, and directed more longitudinally than in the 

 typical species. A. peltastes cannot be a simple variety of ^. tyrannus; still less can the 

 differences be regarded as mere sexual variations. It is a good and distinct species. 



Locality. — Llandeilo Flags. Llandeilo, South Wales ; abundant. Cabinets of 

 Mus. Prac. Geol. (figured specimens 1 to 3) ; of Mr. J. Lee, Caerleon (do. fig. 4) ; Mr. 

 R. Lightbody ; Rev. G. Smith, of Tenby ; and Mr. Edgell, who finds it abundant in the 

 flagstones, while A. tyrannus^ affects the limestone. Also in volcanic grit, Builth, Rad- 

 norshire, and from Abereiddy Bay, Pembrokeshire (Mr. H. Wyatt Edgell). 



AsAPHUS? (B.) HYBRIDUS, U. Sp. PI. XXIII, figS. 8, 9. 



A. [B] modicus, 4 — 5 uncias longus ? complanatus., axe anyustissimo. Cauda, solum cog- 

 nota, roiu7idata semiovalis [long, ad lat. ut % •.1\) axe contracto qudm limbo ter angustiore, 

 vix I longitudinis caudce superante, apice abrupto ohtuso. Sulci axales antice profundi, 



1 The A. tyrannus figured by Hoffman in his summary of the Russ. Tribolites (' Verhandi. Russ. Kais. 

 Min. Gesellsch.,' 18.58, pi. vi, fig;. 3) is a Ptychopyge. The Ogygia Buchii, fig. 4, is a Megalaspis, hke 

 A. heros, Dalm. ! 



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