CONCLUDING REMARKS. 223 



been productive of very interesting results. I refer here especially to Perrin 

 Smith's fruitful studies in the phylogeny of the Glyphioceratidae. 



It may excite some surprise in those who make use of this work that some of 

 the species of Cephalopoda contained in the lists of Irish Carboniferous fossils 

 published by M'Coy, 1 Kelly, 2 Baily, 3 and others, are entirely omitted from its pages. 

 This omission has been found necessary (1) in cases in which the type specimen has 

 been lost and the description found to be insufficient for purposes of identification, 

 (2) more often when the identification of a species has been entirely mistaken. 

 The latter applies to some of the species in the Griffith Collection to which names 

 have been affixed without sufficient discrimination {see foot-note, p. 197). This has 

 been rectified whenever the material was sufficiently well preserved to supply 

 the data necessary for determining the species. 



In comparing the Cephalopod fauna of the Belgian Carboniferous area with 

 that of the British Isles, one cannot fail to notice how few species there are which 

 are common to both. Considering the proximity of the two areas, this is remarkable 

 and difficult to account for, except on the assumption that the physical conditions 

 differed to such an extent as to give a distinctive specific facies, expressed in 

 differing species in the respective areas. 



Without having recourse to comparative tables it may be noted that the species 

 common to the British Isles and Belgium are generally those which are at the same 

 time the most abundant and characteristic of their kind in each area. Such 

 species, e.g., among the Nautiloids are Orthoceras laevigatum, F. M'Coy; Actinoceras 

 giganteum, J. de C. Sowerby; Strobbceras sulcatum, J. de C. Sowerby, sp.; Discitoceras 

 Leveilleanum, L.G. de Koninck, sp.; Apheleceras mutabile, F. M'Coy, sp.; Vestinautilus 

 paucicarinatvs, A. H. Foord. Among the Goniatites the following species may be 

 enumerated in the same sense: — Glyphioceras (Sphenoceras) striatum, J. Sowerby, 

 sp. ; G. ($.) sphsmcum,W. Martin, sp.; 67. (Beyrichoceras) truncatum, J. Phillips, sp. 



Of the rarer forms occurring in both areas the following may be cited :— 

 Trigonoceras paradoxicum, J. de Sowerby, sp.; Temnocheilus coronatus, F. M'Coy. 



Out of 126 species of Cephalopods described by de Koninck (' Calc. Carb.') only 

 about 26 can be identified as occurring in the Irish area. An analysis of these 

 figures shows that out of 52 species of the eoiled Nautiloids 11 are common to 

 Ireland and Belgium, of uncoiled ones 7 out of 11 are common to both countries, 

 and of Goniatites 8 out of 33. 



1 ' Synopsis Carb. Foss. Ireland,' 1841. 



2 ' Joum. Geol. Soc. Dublin,' 1855-7, vol. vii. 

 :; 'Mem. Geol. Surv. Ireland. 1 



