232 ASTRALIUM. 



transversely oval, very oblique, generally golden within, and stained 

 with purple or blue on the columella. Alt. 28, diam. 40 mill. 

 Indian Ocean ; Australia ; Philippines ; New Caledonia; Java, etc. 



Operculum oval, nucleus submarginal ; outside deep bluish-green, 

 excavated around the upper margin and near the middle, edges 

 rugose, center nearly smooth. 



Trochus aculeatus Gmel. is a synonym. 



An extremely variable species. In form it may be either conic 

 with nearly flat base, or flat above with very convex and umbilica- 

 ted base. The spines are generally triangular and obliquely wrink- 

 led above, but are often square and elaborately foliated at the ex- 

 tremities. Restricting the typical calcar to shells with moderately 

 exserted scalariform spire, depressed apex, and body- whorl deflected 

 toward the aperture, we may define several varieties which are typ- 

 ically quite distinct, but which, in the large series before me, are 

 connected with each other and with the type by insensible grada- 

 tions. 



Var. HELICIXUM Gmel. PL 52, figs. 28, 31. 



Last whorl not descending ; spire conical, not much depressed at 

 apex ; marginal spines generally short. Usually larger than the 

 typical form. A specimen before me measures: alt. 40, diam. 70 

 mill. 



Var. LACINIATUM Gould. PL 53, figs. 32, 33. 



Shell bullet-shaped in the adult ; aperture subcircular, white 

 within; columella generally stained with purple. 



Alt. 28, diam. 22 mill. 



Philippines (Goxld), Viti Is. 



Young shells are like var. helicinnm ; the adults are very differ- 

 ent in shape, and sometimes even more elongated than in the figure. 



Var. PLANORBIS Pilsbry. PL 56, figs. 75, 70. 



Spire planulate, scarcely at all exserted ; base very convex, um- 

 bilicated. Alt. 10, diam. 27 mill. 



A curious form, very different from the preceding. 



A. STELLARE Gmel., 1788. PL 55, figs. 66-68. 



Shell imperforate, conoid, solid, more or less elevated, whorls 

 5-6, obliquely radiately costate, imbricately spinose at periphery, 

 the last carinated, carina with about ten long vaulted spines ; base 



