118 GASTEROPODA. 



under the mantle and around the body; anal and generative 

 orifices situated on the right anterior side. Shell univalve, 

 not spiral, concave within, simple, entire, with the vertex 

 anteriorly inclined, and imperforate. 



The anterior side of the shell, is that to which the summit is in- 

 chned, and the impression of the animal's head can easily be distin- 

 guished internally on that side. 



Patella vulgata — The Common Patella, or Limpet. 

 Plate XIV. fig. 15. Oval, conic, or a little depressed; 

 outside green or brown, sometimes radiated with various 

 colours ; having divergent striae and concentric wrinkles ; 

 inside glossy, iridescent, with yellow or fawn-coloured, 

 purple, blue, or brown radiations. Two inches long. In- 

 habits the coasts of Europe. 



Genus 25 CHITON— Zmn^ws. 



Generic Character. — Body creeping, ovate-oblong, con- 

 vex, rounded at both extremities ; marginated all round 

 with a coriaceous skin ; the back covered by a longitudinal 

 series of testaceous, transverse, imbricated, and moveable 

 plates; head anterior, sessile, with the mouth placed below; 

 destitute of tentacula or eyes ; branchise placed in a series, 

 round the body, under the margin of the skin ; anal orifice 

 at the posterior extremity. 



The species of this genus are in much obscurity, and of diflBcult 

 solution. The absence or i)resence of granulations, striae, and punc- 

 tures, are certainly of much use, but the only certain test is an exami- 

 nation of the sides of the valves, which, however, cannot be accom- 

 j.lished mthout taking the specimen to pieces. The sides of the valves 

 are always provided with a certain number of serrated teeth, which 

 seem to afford permanent characters in each species. See Plate I. 

 fig. 11. 



Chiton fascicularis.—THB Fasciculated Chiton. Plate 

 XIV. fig. 13. Eight imbricated valves, nearly smooth, 

 slightly carinated, and rounded at the margins, with thick 

 tufts of hair between the junctions of the valves, there 

 being five on the top of the upper valve, and three on the 

 base of the lower one. Three-fourths of an inch long. 

 Inhabits the British coasts. 



