ACANTHOPLEURA. 231 



Readily recognized by the black, granulated sides, and smoother 

 two-striped ridge, in connection with the peculiar insertion-plate of 

 the tail valves. Smith has placed .the species with doubt in the 

 synonymy of A. spiniger, where it certainly does not belong ; and 

 Martens, also erroneously, suggests its identity with Ch. petholatus 

 Sow. 



The insertion-plate of the tail-valve, while in some specimens 

 somewhat uneven, is not often so serrated as in A. brevispinosa. It 

 further differs from that species in the striped back and the interior 

 coloration. The crescent-shaped black patch behind the sinus inside 

 is square or forked at the ends, as in A. granulata, and the edge of 

 the sinus is white. 



A. BREVISPINOSA Sowerby. PL 47, figs. 18, 19, 20, 21. 



Shell oblong oval, depressed, each valve beaked and concentrically 

 rugose-granulated. Color black, the girdle narrow, clothed with 

 white-tipped black spinelets. 



The valves concentrically wrinkle-grained at the sides of the 

 central areas, and the ill-defined lateral areas are cut into granules 

 by concentric and radiating grooves. End valves finely grooved radi- 

 ally, finely wrinkled concentrically ; mucro posterior, prominent and 

 rather acute. 



Interior blackish-brown or purple-brown except the sutural- and 

 insertion-plates which are' white. Sinus broad, deep, rounded. 

 Anterior valve having* 7-8, central 1, posterior 2 slits and a number 

 of irregular serrations ; anterior teeth moderately long, finely pect- 

 inated outside ; posterior teeth very short, blunt, obsoletely pectinated. 



Girdle rather narrow, clothed with rigid black spinelets tipped 

 with buff. 



Length 42, breadth 26 mill. ; divergence about 130. 



Johanna, Comoro Is. (Cuming, Cpr.) ; Zanzibar (Cpr.) ; Cape of 

 Good Hope and Madagascar (Paris Mus.) ; Strait of Saint Vincent, 

 Cape Verde Is. (Cessac.) 



Chiton brevispinosus SOWB., Mag. of Nat. Hist. 1840, p. 287, t. 

 xvi, f. 1 ; Conchol. Illustr., f. 136. REEVE, Conch. Icon., f. 52. 

 Acanthopleura brevispinosa ROCHEBR., Nouv. Arch, du Mus. 1881, 

 p. 240. 



Part of the localities given above are probably incorrect. A good 

 many shells procured at " Cape of Good Hope" and "Zanzibar" 



