160 GASTROPODA. [Aspidobranchia. 



Genus 3. ASTR^A, Bolten, 1798. 



Astrcea, Bolten. Mus. Bolten. (2), 1798, 79. Type : A. imperialis, Gmel. 

 Astralinm. Link, 1807. Calcar (Montfort), Fischer and other authors ; 

 I operator (Montfort), Auct. ; Trochns (in part) of all earlier authors ; 

 and Tvrlm (in part), Sowerby, jun., and others. 



Animal and radula the same as in Turbo. 



Shell trochiform, generally more or less flattened above or below ; 

 imperforate or umbilicate ; young specimens always carinated and 

 spinose at the periphery. Operculum oval or oblong, usually with 

 submarginal or terminal multispiral nucleus ; the last whorl forming 

 the greater portion of the operculum, usually with 1 or several ribs 

 exteriorly, following the course of the spiral, and most elevated at the 

 distal extremity. 



Inhabiting tropical and temperate seas. 



Fossil. Trias and Tertiary. 



KEY TO SPECIES. 



A. Shell umbilicate, with large spines at periphery .. heliotropium. 



B. Shell imperforate, with small spines at periphery . . . . sulcata. 



Siibgen. 1. ASTR.-EA, s. str. 



Type: A. imperialis, Gmel. Imperator, Montfort, 1810; Canthorbis, Sw<un- 

 son, 1840; and (in part) Gtiildfordia, Gray, 1850. j.-*> 



The central and lateral teeth of the radula bear cusps ; the mar- 

 ginals are not especially large toward the inside. 



Shell large, trochiform, concave and umbilicate below, carinated 

 and spinose at periphery ; whorls convex and granulose above ; oper- 

 culum oval, outside smooth, obsoletely unicostate. 



1. Astraea heliotropium, Marty n, 1784. Plate 41, fig. 1. 



Trochus heliotropium, Mart., Un. Conch., i, 30, not of 1769. Astralinm 

 heliotropium. Mart., Man. Conch. (1), x. 2^S. pi. ."Hi, f. 87. Imperator 

 aureolatus, Montfort, Conch. Syst., 1810. Canthorbix imperialis, Swain- 

 son, 1840. Guildfordia heliophorus, Gray, 18f><>. 



Shell large, depressed conic, widely umbilic;itf. solid, with large 

 triangular spines at the periphery. Sculpture consisting of numerous 

 scaly spiral ribs, obliquely running out to the spines of the periphery 

 on the lower half of the whorls ; base with 3 to 5 strong, scaly, spiral 

 ribs of unequal size ; umbilicus ornamented with strong, oblique 

 growth-lines, which unite on approaching the base, and form a distinct 

 carina. Colour greenish- or bluish-grey, base mostly yellowish. Spire 

 coiioidal, its elevation very variable, about the s;mn> height as the 

 aperture, outlines convex. Protoconch of 2i smooth, flat, and strongly 

 carinated whorls. Whorls 7, first slowly, then rapidly increasing, 

 convex, acutely carinated and produced into long triangular spines, 

 which are hollow, open on the anterior side, recurved, concave above, 

 their number being exceedingly variable, as is also their shape ; base 



