in i"N i: \ Den 1 1 \. 



;ihi>ut 10 trrth liy delirat" .-lit-. Anterinr v:il\- : 

 Tin nil '2 "., poMrrior _'_' -lit.-. Terth even MIL! -harp, -li. 

 -triatrd or grooved outside. Kav.- solid, (lirdle uid , 

 eivd with solid, regularly and closely imlmeat iiiL r -triuted Scales 

 16), Len-th 85, lueadth, 1H mill. 



Monterey, ( 

 c/iifnn regulari* CPB^ P. /. B, 1855, p. 'i'.vi.--l.--'>. l ,<.,,, ( bia 



r I- y n/> m'.* CPB., J/N. 



This species is of a very regular form, and a uniform dral>, -dive 

 or blue color. It is not closely allied to any other West Coast form. 

 Tlu i number of slits in the posterior valve is unusually large. 



I. TIGRINUS Krauss. PI. 19, figs. 60-63. 



Shell oblong, convex, roundly arched, buff-white, unicolored, or 

 striped lengthwise with reddish ; rarely roseate. 



Valves without apices. The lateral areas do not extend to the 

 middle of the back; they are raised, and cut into radiating riblets 

 by 8 or 10 narrow impressed grooves, and there are rather con- 

 spicuous concentric wrinkles or waves of growth on the lower part 

 of the areas. The end valves are similarly sculptured. Central 

 areas closely and regularly pitted all over. Posterior valve rather 

 large and depressed, with subcentral urn bo. 



Interior white and light brown. Anterior valve having 17-18, 

 central valves 2-3, posterior valve 12-13 slits; teeth rather thin, 

 but somewhat bevelled and roughened inside; eaves solid. Sinus 

 wide and flat, the sutural-plates being rounded. Muscle-scars dis- 

 tinctly impressed. 



Girdle rather wide, firm, densely clothed with somewhat coir 

 finely striated scales (fig. 63). Length 22-28 mill. 



Cape of Good Hope. 



Chiton tiyrinus KRAU&S, Die Siidafric. Moll., p. 38, 

 ? Ischnoradsia subcariosa CPR., MS. 



This species is readily known by its Radsioid valvi- and tln> 

 beautiful web-like sculpture of the central areas, produced by the 

 pattern of regularly arranged rhombic pits. It is like no other 

 species, although the young of /. magdaleneiisis bears a slight 

 resemblance in the sculpturing of the central areas. 



Although technically a Radxiella or Stenor' is not easy to 



decide which) this species probably was developed from a different 

 stock of Ischnochitons. Indeed, the multiplication of side-slits may 



