288 MOLLUSCA. BRANCHIFERA. Chiton. 



It is impossible to determine, from the scanty notices which are given by 

 Walker, what was the true character of his P. plana orbiculata margine re- 

 gulariter dentato. The colour white and opake Test. Min. Rar. 5. t i. f. 16. 



EXTINCT SPECIES. 

 I 



1. P. latissima. — Nearly orbicular, flat, smooth, thin; umbo excen trie 



Sower. Min. Conch, t. exxxix. £ 1-5.— In Slaty Clay, Lincolnshire. 



2. P. Imvior — Depressed, conical, smooth, shining ; base obovate ; apex ex- 

 centric — Sower. Min. Conch, t. exxxix. f. 3, 4 Alum Clay, Whitby. 



3. P. cequalis. — Conical, smooth ; base obovate ; back nearly perpendicular. 

 — Sower. Min. Conch, t. exxxix. f. 2 In Cray, Suffolk. 



4. P. rugosa — Depressed, obovate, radiated; apex excen trie, depressed, 



slightly recurved ; back concave above, with reflected undulations Patellite, 



Park. Or. Rem. iii. 50. t. v. £ 21 — Sower. Min. Conch, t. exxxix. £ 6 



In Lower Oolite, Gloucestershire. 



5. P. striata — Oblong, irregularly conical, with numerous acute radii; 



umbo forward, sharp — Sower. Min. Conch, t. ccclxxxix London Clay, Stub- 



bington. 



6. P. lata — Obovate, depressed, nearly smooth, radiated ; radii about 30. 

 distant, rounded ; apex very excentric — Sower. Min Conch, t. cccclxxxiv. 

 £ 1.— Lower Oolite, Stonefield. 



7. P. ancyloidis.— Convex, smooth ; apex spiral ; base oval. — Sower. Min. 

 Conch, t. cccclxxxiv. £ 2 Ancliff. 



8. P. nanus — Obliquely smooth; base oval; apex obtuse Sower. Min. 



Conch, t. cccclxxxiv. f. 3 Ancliff. 



Mr Mantell notices " a small species of Patella of an oval shape, conical, 

 depressed; the casts of the interior of the shell only have been discovered" 

 in Green Sand, Parham Park — Geol. Suss. ^2. 



Gen. XLIII. CHITON. — Shell divided, constituting a series 

 of imbricated dorsal plates, eight in number ; mouth with 

 a semicircular curved membrane above, destitute of tenta- 

 cula. Tongue short, armed with spines. 



* Marginal band with titfts of spines. 



158. C. fascicularis. — Shell oblong, ovate, roughly shao-- 



reened on the sides, with a striated longitudinal mesial stripe. 



Linn. Syst. i. 1106. Mull. Zool. Dan. p. 250. No. 3017. Putt. Dorset, 

 25. Mont. Test. Brit. 5. t. xxvii. £ 5 — On oysters, but not com- 

 mon. 



Length upwards of half an inch, breadth about a quarter ; freckled with 

 green and brown. The granular tubercles are circular, with flat summits ; 

 they are numerous on the sides of the plates, but not on the subcarinated 

 centre. The border is rough, with a spinous margin. The tufts consist of 

 cylindrical, blunt, smooth, solid, calcareous spines of unequal size ; one at 

 the junction of each valve, six on the anteal margin, and two at the retral 

 valve, making twenty in number.— I am inclined to think that the Chiton 



