32 AMPHINEURA. [Polyplacophora. 



SUBORDER 3. TELEOPLACOPHORA, Pilsbry. 



All the valves, or at least the 7 anterior, with insertion plates cut 

 into teeth by slits. 



Fam. CHITONID^J, Pilsbry. 

 Characters of the suborder. 



Subfam. 1. CHITONIN^. 

 ChitonincB, Man. Conch. (1), xiv, 148. 



Regular Chitons, having the insertion plates well developed on 

 all the valves, and closely grooved or pectinated outside and at edge. 



Genus 1. CHITOX, Linnaeus, 1758. 



Chiton, L., Syst. Nat., ed. x, 667. First recognisable species : C. tubercu- 

 latus, L. Chiton, Man. Conch. (1), xiv, 149; xv, 88. Lophyrus (in part), 

 Poli, Test. utr. Sicil., i, 2, 4. Lepidopleurus (in part), Risso. Hist. Nat. 

 Eur. Merid., 267. Gymnoplax, Gray, London Medic. Repos.. xv, 234. 

 (For genera established by Thiele, see Man. Conch., xv, 88.) 



Valves wholly external, the beak of the tail valve median or an- 

 terior ; insertion plates longer than the eaves, slit into teeth which 

 are deeply and finely pectinated, and typically project outward on all 

 the valves. Girdle covered with closely imbricating, convex, smooth 

 or striated scales. Gills extending the entire length of the foot. 



Distribution. World- wide. 



KEY TO SPECIES. 



a. Central areas having longitudinal riblets. 



b. Sides and ridge of central areas both sculptured. 



c. Lateral areas with numerous slightly crenulated 



threads. 



d. Intermediate valves carinated, divergence 120 Quoyi. 

 cc. Lateral areas with 3 or 4 rows of distinct tubercles . . pellisserpentis. 

 bb. Central areas with a smooth band or triangle on ridge of 



each valve, 

 c. Lateral areas with 4-6, pleura with 16 or more, 



granose riblets . . . . . . . . canal ic it I at us. 



cc. Lateral areas with 48 divaricate riblets, pleura 



about 20 furrows on each side. 

 d. Furrows on pleura extended over the whole 



length . . . . . . . . Huttoni. 



dd. Furrows on pleura extended only over half of 



the length . . . . . . . . cereus. 



ccc. Lateral areas with 2-4, pleura 814, nodulose rib- 

 lets. 

 d. Girdle-scales mucronated . . . . . . limans. 



dd. Girdle-scales not mucronated. faintly striated Stangeri. 

 ddd. Girdle-scales not mucronated, quite smooth 



