58 GENERA OF SHELLS. 



Other by their extremities in form of a cater- 

 pillar. 



The valves of the shell, whilst the animal is alive, 

 are separate ; but when dead and contracted, several of 

 them appear to be united. 



C. laevis, striatus. 



Chiton. Shell multivalve, arranged in a 

 single longitudinal series ; valves movable, im- 

 bricate, transverse, lateral extremities con- 

 nected by a folding back of the mantle. 



The shell is generally composed of eight valves ; 

 sometimes of seven, or only six ; the middle valves are 

 longer than those at the extremities. 



C. gigas, squamosus, Peruvianus, spinosiis, fascicularis, 

 marginatus, Magellanicus. 



Patella. Shell univalve, not spiral, shield- 

 like, or like a depressed cone ; concave and sim- 

 ple beneath, margin without fissure, summit 

 entire, inclined anteriorly. 



The patellee are widest at the posterior side, and the 

 outline of the shell is generally oval. Most of them 

 have ribs, radiating from the summit to the margin. 



P. apicina, granatina, oculus, barbara, plicata, laciniosa, 

 saccharina, angulosa, baibata, longicosta, spinifera, aspera, 

 luteola, pyramidata, umbella, plunibea, coerulea, radians, 

 scutellaris, Safiana, testudinaria, cochlear, compressa, gran* 

 ularis, deaurata, Magellanica, stellifera, vulgata, rnamillaris, 

 lineata, leucopleura, notata, Tarentina, punctata, punctu- 

 rata, Javanica, tiiberculifera, niiniata, viriduJa, pectinata, 

 Galathea, pellucida, tricostata, australis, cymbularia,— ^ 

 .'iraœna, alternata. 



