B. Bullen Neicton — On Archanodon Jukesi. 245 



species of this genus, which have been described above, show that it is 

 a generalized form, and suggest the idea that Phillipsia is separable 

 as a distinct genus from Froetus more for stratigraphical than 

 morphological reasons. 



EXPLANATION OF PLATE X. 



Fig. 1. Fhillipsia cracoensis, n.sp. Central portion of head-shield, x 3. 



2. ,, ,, ,, Central portion of another head-shield, x 3. 



Pygidium. x 3. 

 Another pygidium. x 3. 

 Free cheek, x 3. 

 Hypostome. x 3. 

 Outline restoration of head-shield. 



IL— On Arcranovon Jukesi (Forbes MS.), Baily, sp., from the 



Old Ked Sandstone of Monmouthshire. 



By R. Bullen Newton, F.G.S. 



Introduction. 



THROUGH the kind intervention of Professor H. G. Seeley, 

 F.R.S., some few years since, Mr. Percy Hawkins was induced 

 to present to the Geological Department of the British Museum 

 a slab of Old Eed Sandstone from Llanvaches, nearly midway 

 between Caerleon and Chepstow, Monmouthshire, containing some 

 excellent impressions of Archanodon Jukesi. 



Originally found in Ireland, and since reported from Northumber- 

 land, the present notice of the shell forms a second record of its 

 occurrence in Britain. So far as our knowledge extends, it remains 

 the most ancient lacustrine or fluviatile bivalve mollusc yet known in 

 the British Islands, and on that account, coupled with its great rarity, 

 it is hoped that the following account, dealing with its discovery in 

 Western England, may lend an additional interest to the species. 

 Before entering upon this, however, it may be of advantage to 

 submit a brief summary of the literature relating to this organism. 



Bibliographical Review of Archanodon Jukesi. 



The first reference to this mollusc was made by Edward Forbes^ 

 in 1853 in a provisional list of fossils characterizing the 'Yellow 

 Sandstone' at the hill of Knocktopher, co, Kilkenny, Ireland, which 

 included plants (Cyclopteris Hibernicus, Lepidodendron, and Stig- 

 maria), fish (Hotoptychius), Crustacea (Pterygotus), and a 'large 

 bivalve shell,' to which was given the name of Anodon Jukesi. 

 These forms of life were recognized as indicative "of fresh or at 

 least brackish water conditions at the period of the deposition of 

 the beds." 



In 1857 J. B. Jukes and J. W. Salter ^ referred to the occurrence 

 of Anodon Jukesi in the Yellow Sandstone of Kiltorcan Hill, near 



1 Edward Forbes, " On the Fossils of the Yellow Sandstone of the South o«f 

 Ireland" : 22nd Rep. British Assoc, for 1852, published 1853, p. 43. 



^ J. B. Jukes and J. "W. Salter, " Notes on the Classification of the Devonian and 

 ■Carboniferous Rocks of the South of Ireland" : Journ. Geol. Soc. Dublin, vol. vii 

 {1857), p. 63. 



