ASAPHUS. 149 



to the typical Asapld than Basilicus, a subgenus having the facial suture marginal in front 

 like Ocjygia, but yet having the deeply lobed labrum of the typical forms. 



Lastly Ftychopyge, of which we have no certain representative in Britain/ has the 

 aspect of the Oyygia ; and even its intramarginal suture finds its parallel in the 

 0. {Oyyyiocaris) dilatata, Dalm. Yet having the labrum strongly notched, it may for 

 the present be safely included in Asaphus. 



Subgenus 2. — Basilicus, 1849. 

 1. AsAPHus (Basilicus) Tyrannus, MurcJnson, Plates XXI and XXII, figs. 5 — 12. 



Asaphus Tyrannus, Murchison. Silurian System, pi. xxiv, fig. 4, pi. xxv, fig. 1, 1837. 



— — Milne-Edwards. Crustac^s, vol. iii, 310, 1840. 



— — Emmerich. Leonhard und Bronn's Jahrb., 184.5. 



— — Salter. Decade ii, Geol. Surv., pi. v, 1849 (1848). 



— — Id. Morris's Catalogue, ed. 2, p. 100, 1854. 



— — Id. Siluria, ed. 2, pi. 1, fig. 5, pi. ii, fig. 1, 1859. (Not of 



Burmeister, Org. Trilob., t. 5, fig. 4, which is A. heros). 

 Ogygia Tyrannus, Emmerich. Dissert. (1839). 



Asaphus Tyrannus, Id. Leonh. und Bronn's Jahrb., p. 42, 1845. 



IsoTELUS Tyrannus, M'Coy. Synops. Woodw. Pal. Foss. Fasc. i, p. 171, 1851. 

 Asaphus Tyrannus, Salter. App. Ramsay, Geol. N. Wales ; Mem. Geol. Surv., 



vol. iii, p. 312, pi. xiii, fig. 1 — 6 (1866 ined.) 



A. magnus, interdum pedalis, ovatus fere, per-sculptus ; capite ohtuso quam caudd 

 elongatd breviore. Oculi depressi approximati, sese spatio glabella longitudinis remoti. 

 Glabella brevis pyriformis, lobis lateralibus supra oculum distinctis. Anguli capitis breves. 

 Cauda parabolica, apice iruncato, axe multi-annulato, lateribus muUicostatis, costis 12 — 13 

 abbreviatis. 



Sir Roderick Murchison hit upon a happy name for this fossil, the largest then known 

 among British Trilobites, and singularly plentiful in the region which he made his own by 

 hard work along the South Welsh frontier. It is not only our finest British species, but 

 is peculiarly British, and even restricted to the Welsh Principality and the border-counties. 

 Often as it has been quoted out of Britain, it has never, except in one single locality (in 

 North Wales), been really found outside the restricted area of Shropshire and South 

 Wales, where, as above said, it may be counted in swarms. Earl Cawdor's magnificent 

 specimen found in Dynevor Park, Llandeilo, is here again figured from the British 

 Museum collection, with others, of smaller size, from the Museum of Practical Geology. 

 It is the best of types, together with the Ogygia Buchii, for the Llandeilo rocks proper, 



1 It was an error to insert this subgeneric name under Ogygia corndensis, p. 130. That is a true 

 Ogygia. It is just possible A. radiatus, p. 154, may belong to it. 



