TONICELLA. 43 



cially in the posterior valve, and blunt, in adults decidedly crenu- 

 lated at the tips and obsoletely fissured outside. Eaves small. 



Girdle leathery, apparently smooth and nude, brown in dried 

 specimens. 



Gills extending forward two-thirds the length of the foot, com- 

 posed of 27 branchiae each. 



Length 37, breadth 20 mill. 



Length 30, breadth 15 mill. ; divergence 120. 



From Bering Strait southwestward to the Okhotsk Sea and Japan, 

 southeastward to the Bay of Monterey, California. Aleutian Is. 



Chiton lineatus WOOD, General Conchology p. 15, t. 2, f. 4, 5, 

 1815 MIDD., Mai Ross, i, p. 109, t. 12, f. 8, 9. SOWB., Conch. 111. 

 f. 77. REEVE, Conch. Icon. t. 7, f. 33. Tonicia lineata Wood, H. 

 & A. AD., Genera Rec. Moll, i, p. 474. Tonicella lineata CPR. MS., 

 p. 38. DALL, Proc. U. S. Nat. Mus. 1878, p. 326. 



In many old specimens of this species the teeth are distinctly, 

 though obsoletely crenulated and striated outside, presenting an 

 approach to Tonicia. The slit in the median valves frequently has 

 its edges thickened, and there is a distinct notch on each side of it. 



This is one of the handsomest north Pacific Chitons. It is read- 

 ily distinguished from T. marmorea and T. submarmorea by the 

 absence of microscopic granulation of the surface, as well as by the 

 pattern of coloring. Dall writes : 



The painting of this very characteristic species is very variable, 

 even on different valves of the same individual. Nothing can 

 appear more distinct than the coloration of typical specimens of 

 some varieties, but in a large series the differences do not hold 

 equally good. The number of slits is also somewhat variable, occa- 

 sional abnormal or injured specimens having only six or seven slits 

 in the tail valve. But fine and normal specimens of both varieties 

 show no more than individual variations. 



Middendorff, while pointing out the distinctions between the fol- 

 lowing species and T. marmorea, appears to have overlooked the 

 connection between the former and T. lineata and his description 

 does not always agree with his figures. 



From Tonicia lineolata Sowerby, from South America, besides the 

 internal generic characters, the exterior differs by the absence of 

 punctures and raised granules at the sides. 



