96 BRITISH FOSSIL CRUSTACEA. 



These strata furnish occasionally the remains of the carapace of Plerygotus, which I have 

 myself seen there in the same slabs with Platgschisma helicites, and the characteristic 

 Chonetes lata. 



At Bradnor Hill, near Kington, the lane which leads to the hill from Newton exposes 

 what I consider to be the summit of the Upper Ludlow rock, and the Bone-bed associated 

 with its upper layers. These beds contain true Upper Ludlow fossils, as Cornulites 

 serpularius, Platgschisma helicites, Chonetes lata, Bhgnchonella nucula, Orbicula rugata, 

 and Orthoceratites of two or three species, and which are not found in the overlying Passage- 

 beds proper. Remains of Pterygotus also occur in these strata. 



6. — Passage-beds. 



The transition- or " Passage-beds" between two great formations often furnish a series of 

 fossils of the highest value to the palaeontologist, and the Passage-rocks between the 

 Upper Silurians and the Lower Old Red Sandstone are no exception to this rule. The 

 occurrence of large Crustacea other than Trilobites in the older rocks was hardly known 

 until about the year 1855, when discoveries were made in Scotland and Siluria of 

 several new forms of fine Crustacea, which have been described by Salter, Huxley, and 

 more lately by Woodward. In many localities these remains of Crustaceans are accom- 

 panied by the relics of Fishes, such as Pteraspis (the oldest form of which has been found 

 in the Lower Ludlow beds, below the Aymestry Limestone), Cep/ialaspis, Auchenaspis, 

 and Onchns, two of which forms, Pteraspis and Onchus, range from Silurian deposits into 

 the Middle Old Red, for remains of both these genera have been detected in rocks above 

 the <f Cornstones." As, however, the characteristic Silurian shells do not appear in any 

 quantity above the "Bone-bed,'' for convenience sake I place the base of the "Passage-beds" 

 at the " Bone-bed," inclusive. I include in the " Passage-beds " all the strata from the 

 summit of the Upper Ludlow Rock proper to the micaceous flags and red marls which herald 

 in the Old Red proper, and which contain traces of Cephalaspis Lyellii and Scaphaspis 

 Llogdii, two Fishes abundant in the overlying Cornstones. 



It was in 1854 or the commencement of 1855 that my friend Mr. Richard Banks, of 

 Ridgebourne, Kington, first directed my attention to the remarkable collection of fossils he 

 had obtained from several localities in that neighbourhood. I acquainted Sir R. Murchison 

 with the fact of their discovery, and papers were subsequently published in the Journal of 

 the Geological Society and in the 'Edin. New Phil. Jour.,' by Mr. Banks, Sir P. Egerton, 

 Sir R. Murchison, Mr. Salter, and myself, with descriptions of the fossils and their position 

 in the strata in which they were discovered. (See ' Edin. New Phil. Jour./ April, 1855, and 

 Oct., 1856. Also ' Quart. Journ. Geol. Soc.,' May, 1856 ; and March 25, 1857, &c.) 



In addition to the discovery of some new forms of Fish, Mr. Banks found the relics 

 of several Crustaceans, such as Pterggotus and Eurypterus ; but on visiting the 



