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, Acantliojjleura, 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 scutae 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. Chiton fascicularis (?). Linn. Tab. XX, fig. 9, a — h. 



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



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



— G. Soxo.jun. Conch. lUust. fig. 87-87a, 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 stibcarinatd, anfjulatd ; valvarum carinis longitudinaliter striatis ; lateribus 

 mibjjlanis, 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 quincun.x 

 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. crinitus, 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 striae, like those upon the recent C. fascicularis. 



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