142 WORMS. TE8TACEA. 32. Chiton. 



tures ; the pieces covered with small tubercles sup- 

 porting the spines. 



$r. Zool. I. 34. Barbut. t. 1 1 ./. j . Shaw. Misc. t. 223. 



Shell reddish or yellowish : fpines short, violet, losing their 

 colour and falling off when dead : pores in about 3 rows : tubercles 

 pale, furrounded with a circle of lefser-ones: vent clofed by a co- 

 riaceous membrane covered with fpines. 



2. Lefs, deprefsed at top, with narrower futures. 

 faster, cp. subs. 3. p. \ 1 2. t. 1 1 .f. 2-8. 



Shell with fewer tubercles, and a ferrate line down the middle of 

 the pieces : pores of the futures in alternate rows of 2 or 3 foramina. 



145. Ech. Cidaris. Hemisphasrical, depressed, with 5 

 flexuous linear sutures ; the pieces alternately bifari- 

 ous. 



Scotland. Sowetby Brit. Miscell. t. 44. 



Shell a compressed globe : the pieces granulate, with 2 rows of 

 alternate protuberances furnished with perforated papillae, fur- 

 rounded with a circle or two of granulations, and feparated by a 

 groove running round them : fpines elongated, granular, in 2 rows, 

 with 2 rows of fmaller-ones at their bafe : mouth covered with im- 

 bricate obtufe fpines. 



B. Vent underneath. 



146. Ech. lacunosus. Ovate, heart-shaped, gibbous, with 

 5 depressed ovate porous sutures placed in a stellate 

 manner. 



Er. Zool. iv. t. 35. Barbut. t. 1 1./. 8. 



Shell purple at top ; the fpaces between the futures tubercled ia 

 vraved rows; beneath studded and' divided by 2 fmooth fpaces ; 

 fpines very long, mixed with shorter-ones. 



l4t." Ech. Spatagus. Ovate, a little heart-shaped, gib- 

 bous, with 4 depressed porous grooved sutures pla- 

 ced in a stellate manner. 



Er. Zool. iv. t. 34#/. 75. Barbut. t. \\.f.-j. 



Sheltextremely brittle, gibbous at one end, and marked by a deep 

 gfoove instead of the fifth future at the other, tubercled beneath: 

 fores in a double row along each side of the grooves : fpines slen- 

 der, bristle-like. 



ORDER III. TESTACEA. SHELLS. 



A. With more than two valves. 

 38. CHITON. 



148. Ch. marginatus. With 8 smooth valves, reflected 

 and serrate on the margin, carhiate down the back. 



Br. Zool. t. 36.7. 2. Barbut, t. i.f. 4. 



Shell 6 lines long and 4 broad, grey or brown, fometimes mottled, 

 oblong-oval, rough on the furface : valves imbricate over each 

 other in a point, 



149. Ch. tevis. With 8 smooth valves, even on the mar- 

 gin, carinate and beaked on the back. 



Brit. Zool. t. 36.7.3- 



Shell oblong, half an inch long and a quarter broad, deep rufous- 

 'brown, fometimes mottled with yellowish-white, with mostly a 

 pale line down the back, fometimes finely striate tranfverfely ; the 

 iriaVgin broad and finely reticulate : valves beaked in the centre. 



