62 ISCHNOCHITON. 



still to see specimens truly connecting the three forms, although 

 they are doubtless closely allied. The present form differs from 

 magdalenensis in having a concave head valve, strong, distinct, 

 acute riblets upon the central areas, and a generally more robust 

 growth. 



J. conspicuus also has a concave head valve, but the sides of the 

 central areas show no sculpture except microscopic granulation, 

 and the scales of the girdle are pulled out into true spines or bris- 

 tles. 



There is a light form of acrior which is fleshy-white, the girdle 

 gray-white or dark ; and some of these have the jugum or the cen- 

 tral areas of the normal green-olive color (fig. 89.) 



I. MAGDALENENSIS Hinds. PI. 15, figs. 98, 99, 100. 



Shell elongated, rather narrow, generally faintly mottled with 

 delicate olive on a light greenish, blue or pinkish ground. Interior 

 bluish, white or pink. Lateral areas and end valves having radia- 

 ting riblets, central areas finely pitted. 



The lateral areas are distinctly raised, radiately delicately ribbed. 

 Front slope of the anterior valve straight. Central areas having a 

 more or less developed system of branching reticulating wrinkles pro- 

 ducing oblong or diamond-shaped pits. Umbo of posterior valve 

 central, but little projecting. 



Interior : Sutural plates well developed, the sinus deep, angular. 

 Anterior valve having 10-13, central valve 2-4, posterior valve 

 10-12 slits. 



Girdle having fine, close, solid imbricating scales. 



Length 75, breadth 30 mill. ; divergence about 130. 



Length 55, breadth 27 mill. 



Monterey, California, south to Magdalena Bay ; Catalina and. 

 Sta. Barbara Is. 



Chiton magdalenehsis HINDS, Zool. Voy. 'Sulphur' ii, p. 54, t. 

 19, f. 1. REEVE, Conch. Icon. t. 5, f. 20b. Stenoradsia magdalen- 

 ensis CPR. S. " magdalensis " KEEP, West Coast Shells, p. 107, f. 

 94, and of collectors generally. 



This species differs from I. conspicuus in its pitted instead of finely 

 granulose central areas and in the mantle-covering of minute, solid 

 scales, unlike the short spines of the other form. It differs from /. 

 acrior in the much finer sculpture and more delicate coloring. 



