GASTEROPODA. 185 



the soft parts of the animal, while the colour of the valves was also considered a 

 distinction. 



In the ' Zool. Journ.' for 1829, the Rev. Lansdown Guilding divided the Fam. 

 Chitonida (Gray) into five genera, viz., Chiton, Acanthopleura Phakellopleura, Chito- 

 nellus, and Cryptoconchus. 



As three of these are distinguished by the ornamental markings and appendages 

 upon the coriaceous margin or zone which surrounds the shell, and the remaining 

 two depend upon the position of the cerames or scutas on the back of the animal, 

 they possess an artificial character of no great value in the determination of fossils. 

 Mr. Gray, in the Proc. of the Zool. Soc, 1847-48, has given a new arrangement of 

 this family, and divided it into twenty genera. 



1. Chitox fasciculaeis (?). Linn. Tab. XX, fig. 9, a — 5. 



Chiton fascicularis. Linn. Syst. Nat. p. 1106, 1766. 



— Chemn. Conch, x, t. 173, fig. 1688, 1780. 



— G. Sow.jun. Conch. Illust. fig. 87-87«, 1841. 



— Phil. Enum. Moll. Sic. vol. i, p. 108, t. 7, fig. 2, 1836. 



— S. Wood. Catalogue 1842. 



— Morris. Catal. of Brit. Fossils, p. 142, 1843. 



Ch. Testa subcarinatd, angulatd ; valvarum carinis longitudinaliter striatis ; lateribus 

 suhplanis, compressis, granulatis. 



Shell subcarinate, angular ; the central part or keel longitudinally striated ; sides 

 rather flat, covered with depressed granulations. 



Dimensions (?) 



Locality. Cor. Crag, Sutton. Recent, Britain. 



I have but a few valves of this species, and those are not in good preservation. 

 The sculpture and ornaments appear to correspond with the well-known recent 

 British species, but the valves are more elevated and angular, and have a sharper 

 back than any of my recent specimens. The sides of the fossil valves diverge at 

 an angle of less than 90°, and the length is nearly equal to the breadth of one of 

 the sides. The sustentacula or apophyses in all my specimens are unfortunately 

 imperfect. There is generally in the recent specimens a considerable flatness in the 

 anterior part of the dorsal area produced by the action of the posterior projecting 

 umbo of the antecedent valve. The granules upon the lateral areas are large, and 

 more or less elongato-oval, increasing in size from the young shell or umbo to the 

 sides, and appear placed in irregular quincunx order. A curved, diverging linear 

 arrangement may be observed in some specimens, and these granules are quite flat 

 on the top, like those of Ch. fascicularis, and are larger than those upon Ch. crinitiis, 

 and the valves are elevated. The Crag shell has characters that appear to unite 

 the two. Better specimens than those I possess are necessary to determine the 

 true character. The dorsal area has what appear to be punctured strise, like those 

 upon the recent C. fascicularis. 



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