154 CHITON. 



interrupted and broken, and bearing a few low tubercles. Central 

 areas smooth along the ridge, the sides sculptured with longitudinal 

 riblets curving inward, becoming coarser outwardly and diverging. 

 End valves closely tuberculate all over, the pattern resembling that 

 of an engine-turned watch case. Umbo of tail valve near the front 

 margin. 



Interior blue-green, very smooth, the sutural plates lighter; sinus 

 narrow, toothed. Anterior valve having 13, central valves 1, pos- 

 terior valve 14 slits; teeth blunt, pectinated. Slit-rays hardly or not 

 punctate. 



Girdle white, buff or light green, alternating with patches of dark 

 green or blackish. Scales rather coarse, convex, polished. 



Length 60, breadth 33 mill, (average Jamaica specimen.) 



Length 90, breadth 55 mill, (specimen from Nassau, N. P.) 



Bermuda, Florida and Texas to Trinidad. 



Chiton tuberculatus LINNE, Syst. Nat. x, p. 667 (1758). 

 HANLEY, Shells of Linn., p. 12. Chiton squamosus BORN, Test. 

 Mus. Cses. Vindob., p. 5, t. 1, f. 1. CHEMN., Conchyl. Cab. viii, 

 f. 788-790. REEVE, Conch. Icon., t. 3, f. 16. HADDON, Chall. 

 Polyplac., p. 20, and of all modern authors. NOT Chiton squamosus 

 Liune. Chiton undatus SPENGLER, Skrivter af Naturhist. Selska- 

 bet iv, p. 68 (1797). C. bistriatus WOOD, Gen. Conch., p. 7 (1815). 

 f C. tessellatus WOOD, 1. c., p. 23. 



This species has been generally considered to be the squamosus of 

 Linnseus, but that the Linnsean name belongs to another species 

 must be regarded as established. The references quoted by Linnseus 

 in the tenth edition of [the Systema clearly show that this is the 

 species which he called tuberculatus. In the twelfth edition other 

 references not applicable to the species are added ; and the figures 

 given by Chemnitz, Born, and others under the incorrect name 

 " squamosus " have caused subsequent authors to adopt the latter 

 name. 



This species is the commonest Chiton of the West Indies, and is 

 readily known by its (typically) strong, curved ribs and peculiar 

 sculpture upon the enc^valves, which Reeve aptly compares to that 

 of a lathe-turned watch case. It is extremely difficult to draw a 

 line between this species and C. assimilis of Reeve ; so difficult, in 

 fact, that I have been unable to satisfactorily distribute a portion of 

 the specimens before me between the two. Linnreus describes tu- 



