DINOPLAX. 255 



anterior valve not corresponding to external ribs. Posterior valve 

 having the mucro, posterior. Sutural plates broadly united across the 

 sinus. Girdle thick, leathery, with minute bunches of delicate spine- 

 lets scattered upon it. 



The position assigned by Shuttleworth to the type of this genus 

 was not far from correct. The Ischnoid insertion-plates, solid eaves 

 and the leathery spiculose girdle are characters strongly binding 0. 

 gigas to Chcetopleura. Upon parting the valves, however, we notice 

 that the mucro in C. gigas is situated toward the rear, and the pos- 

 terior teeth are thereby thrown forward, as in Pallochiton ; the 

 sutural plates are united by a brown " keystone " filling the sinus 

 somewhat as in Eudoxochiton (p. 192) ; and the spicules of the girdle 

 are gathered into little bunches different from any other Chiton. 

 The valves, too, are remarkably solid. This combination of char- 

 acters seems sufficient for the establishment of the genus Dinoplax, 

 the position of which I take to be near Pallochiton. 



D. GIGAS Gmelin. PI. 57, figs. 21-32. 



Shell oval, large, ponderous and strong, elevated, obtusely angled. 

 Surface lusterless, eroded, ash-white in color with some brown 

 smears, when adult ; the young being prettily streaked or mottled 

 with chestnut and bluish on a light ground. 



Median valves not beaked ; lateral areas very much elevated, 

 radially striated in young shells and upon the outer edges of adults ; 

 central areas closely and finely foveolate in the young, and on the 

 protected front edge of adult valves. Anterior valve elevated, its 

 surface similar to the lateral areas. Posterior valve depressed but 

 roof-shaped, the mucro posterior, the slope behind it nearly vertical. 



Interior whitish, flesh-colored on the sutural plates and marked 

 with brown at their bases ; having two broad chestnut rays behind. 

 Sutural plates wide, connected across the sinus by a broad key-stone 

 shaped lamina. Anterior valve having 8-10, central valves 1, pos- 

 terior valve 8-10 slits ; teeth acute, smooth, those of the posterior 

 valve rather stumpy, wedge-shaped, directed forward. Eaves solid. 



Girdle fleshy, strong, blackish, beset with numerous tiny bunches 

 of minute spinelets (fig. 31.) 



Length 70, breadth 45 mill. 



Length 100, breadth 56 mill. 



South Africa, at Table Bay, Natal, Port Elizabeth and Algoa Bay. 



Chiton maximus a Promontorio Bonce Spei CHEMNITZ, Von einem 

 Geschlechte vielschalichter Conchylien mit sichtbaren Gelenken, 



