PALAEONTOLOGY 



modern Port Jackson sharks (Cestraciontidae), characterized by the fusion 

 of their crushing teeth into spirally twisted oblique plates. The first- 

 named species, which is the sole representative of its genus, appears to 

 have been founded on the evidence of teeth from Staffordshire, where it 

 occurs at Longton, Fenton, and Silverdale, but the second seems to be 

 typically from Northumberland. The existing Cestraciontidae have a 

 Staffordshire representative in the form of Spbenacantbus hybodoides, a 

 member of a widely spread extinct genus with several species. Within 

 the county it occurs at Longton and also near Dudley. 



The other Staffordshire elasmobranch fish is Acanthodes ivardi, which 

 takes its specific title from the late Mr. John Ward, of Longton, who did 

 such good work in collecting and describing the fossil vertebrates of the 

 county. It is a member of the Palaeozoic group Acanthodii, charac- 

 terized among other features, by the persistent notochord, and the pres- 

 ence of prominent dermal appendages to the gill-arches, which during 

 life probably carried flaps of skin ; from this character the members of 

 the group have been called fringe-gilled sharks. Acantbodes includes 

 several other species, but A, ivardi occurs typically in the Deep-Mine 

 Ironstone of Longton, although it is also known from the Scottish Coal- 

 fields. A species of the allied genus Acantbodopsis from the Woodhouse 

 Coal of the Cheadle Coalfield has been described by Dr. R. H. Traquair 

 in the Annals and Magazine of Natural History for 1894 16 as A. microdon, 

 on the evidence of a specimen now in the British Museum. 



In addition to the foregoing, certain fin or dorsal spines of sharks or 

 chimaeroids have been recorded from the Coal Measures of the county 

 belonging to so-called genera of which the precise systematic position 

 cannot at present be determined. Such is Gyracanthus formosus, widely 

 distributed in the British Coalfields, and occurring in the county at 

 Fenton. Another type is Euctenius unilateralis, originally described from 

 a Lanarkshire specimen. Greater interest attaches to two masses of rock 

 discovered by Mr. John Ward in the Middle Coal Measures of North 

 Staffordshire containing numerous species of the doubtful type long 

 known as Listracantbus. These have been described by Dr. Smith 

 Woodward, 17 and are made the type of a new species, Listracantbus wardi. 

 From these specimens it appears evident that the Listracantbus spines 

 are strangely modified dermal tubercles occurring in considerable numbers 

 on part at least of the head and body of the fish to which they pertain. 

 They are identical with at least some of the structures from the Coal 

 Measures of Indiana, U.S.A., described as Petrodus. 



With Ctenodus cristatus and Ct. murchisoni we come to two well- 

 known representatives of the typical genus of the Carboniferous family 

 Gtenodontidae^ which belongs to the sub-class of Dipnoi, or lung-fishes, 

 and takes its name from the somewhat comb-like structure of the fine 

 ridges on the large and flattened palatal teeth. The first species is 

 recorded from Hanley and Tunstall, and the second from the Bassey Mine 

 Ironstone of the Middle Coal Measures. 



16 Ser. 6, xiv, 372 (1894.). " Geol. Mag. (4), x, 486 (1903). 



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