HELCIONISCUS. 145 



or split into several narroiv stripes. The rays are generally eleven 

 in number, but often some of them are multiplied by splitting. 



Interior yellow (or silvery), showing the rays as vividly as the 

 outside; the central area red-chestnut in color. 



Suez and Mozambique (Reeve) ; Madagascar (Dall) ; Reunion 

 (Nevill, in Phil. Acad. Colin.). 



Patella rota, testa suhrotunda, etc., Chemn., Conchyl. Cab. x, p. 

 330, t. 168, f. 1619.— P. rota Gmel., Syst. Nat. xiii, p. 3720.— 

 Reeve, Conch. Icon. f. 39a. — Helcioniscus rota Dall, Amer. Jour. 

 Conch, vi, p. 278, pi. 16, f. 28. — Patella variegata Reeve, Conch. 

 Syst. t. 136, f. 1. — P. petalata Rve., Conch. Icon. f. 56. — P. luzonica 

 RvE., I. e., f. 86.— P. scalata Rve., /. c, f. 89.—? ? P. argentaurum 

 Lesson, Voy. de la Coquille, p. 414. 



An excessively variable species. It is closely allied to P. novem- 

 radiata, but in that species the rays do not bifurcate, although 

 they are often split into two, and the indistinctly defined central 

 callus is white with more or less bright yellow tint. It is even more 

 closely allied to P. capensis Gmel and P. variabilis Krauss, and the 

 three may prove to be one species, although in some details they 

 differ. I have seen too few of the Cape species to write confidently 

 upon their constant characteristics. 



Var. ROTA, typical, (figs. 65-69) may be restricted to the forms 

 with chestnut or reddish spatula. As a synonym I have placed 

 P. variegata Reeve, founded upon a typical specimen of rota, 

 although Reeve afterward shifted the name to a different sjiecies. 



The following seem to belong here : 



P. petalata Rve. (pi. 72, figs. 70, 71). "Shell ovate, rather de- 

 pressed, obsoletely cancellately ridged ; transparent yellow, painted 

 with broad blackish-purple rays. Interior transparent horny, 

 nucleus chestnut-purple. Australia." {Reeve.') 



P. luzonica Reeve, (pi. 72, figs. 72, 73). " Shell rotuudately ovate, 

 rather depressed, radiately finely ridged, ridges granuled ; apex 

 sharp, anterior minutely hooked ; ti'ansparent yellow, rather horny, 

 promiscuously stained with large black blotches. Interior trans- 

 parent, subiridescent, dark chestnut in the middle. Luzon, Philip- 

 pines." (Rve.) 



P. scalata Rve, (pi. 72, figs. 74, 75). " Shell ovate, rather sharply 

 convex ; apex scarcely central ; radiately obtusely striated, and 

 here and there linearly grooved ; livid-white, rayed with black 

 10 



