202 PERMIAN FOSSILS. 



Family Chitonid^ {Les Oscabrions), Cuvier. 



The genera of this group are furnished with a row of shelly plates placed on the 

 back of the mollusk, and extending from the head to the tail. The Rev. Lansdown 

 Guilding^ and Mr. J. E. Gray, but more particularly the latter,^ have instituted for the 

 recent species a number of new genera ; and considering the modifications presented by 

 extinct forms, particularly protozoic species, which are, unexpectedly, rather abundant, 

 it is extremely probable, that many more will be hereafter added. Mr. J. W. Salter 

 has already made a beginning among the latter, by proposing the genus Ilelmintho- 

 chiton for a singular fossil discovered by Dr. Griffith in the Silurian beds of county 

 Galway.^ Probably the fossil immediately to be described belongs to one of the many 

 genera proposed of late by Mr. J. E. Gray ; but, in the absence of precise knowledge 

 on the subject, I am compelled to collocate it as follows. 



Genus Chiton^ Linnaeus, 1758. 



Diagnosis. — " Shell divided, constituting a series of imbricated dorsal plates, eight 

 in number ; mouth with a semicircular curved membrane above, destitute of tentacula." 

 (Fleming.*) 



Chiton Loftusianus,* King. Plate XVI, figs. 9, 10, 11, 12, 13, 14. 



Chiton, King. Ann. and Mag. Nat. Hist., vol. xiv, Nov. 1844. 



— „ London Geological Journal, vol. i, p. 10, figs. 1-4, 1846. 



— LoFTUSiANUS, King. Catalogue, p. 12, 1848. 



— „ Howse, Trans. T. N. F. C, vol. i, p. 242, 1848. 



Diagnosis. — Plates somewhat thick ; marked with incremental lines on the lateral 

 areas, which, together with the dorsal areas, are also finely granulated exteriorly. 

 Dorsal or intermediate plates — some (? 2d) long in the middle, the posterior margin of 

 which is pointed, and the anterior straight — others (? 4th, 5th, and 6th) short, projecting 

 behind, and deeply sinuated in front. Cephalic plate with the apex elevated; slightly 

 sinuated in front. Caudal plate capuliform ; apex nearest the anterior margin, which is 

 slightly sinuated, — also the posterior margin. Apophyses rather projecting; with a 



^ Zoological Journal, 1829. 



2 Ann. and Mag. of Nat. Hist., vol. xx, p. I5l ; and Op. cit., 2d series, vol. i, p. 228. 



3 Vide ' A Synopsis of the Silurian Fossils of Ireland,' pp. 71-2 ; and ' Quarterly Journal of the Geological 

 Society,' vol. iii, part i, pp. 48-52. 



"• British Animals, p. 288. 



^ This species is named " after Mr. W. K. Loftus, to whom I was first indebted for the idea, that it be- 

 longed to the genus Chiton." (King, Catalogue, p. 12.) 



