394 CALLIOSTOMA. 



Maine Northward ; Scandinavia ; N. Scotland ; fossil in the English 

 Crag. (40-90 fms.) 



Trochus occidentalis MK;II. A: AD., Best. Journ. Nat. Hist, iv, p. 

 47, t. 4, f. 16 (1841). JEFFREYS, Brit. Conch, iii, p. 333 ; v, t. 63, 

 f. 7. GOULD, Invert, of Mass., ed. Binney, p. 286, fig. 548. Margar- 

 ita alabastrum Beck, in LOVEN, Ind. Moll. lit. Scandin., p. 20 (1846). 

 T. alabastrum Beck, PIIIUIMM, Conchyl. Cab., p. 91, t. 15, f. 14. 

 FORBES & HANLEY, Hist. Brit. Moll, ii, p. 4 ( J7, t. 66, f. 7, 8. 

 Tr. formosus FORBES, Ann. Mag. Nat. Hist, xix, p. 96, t. 9, f. 1 

 (1847). SEARLES WOOD, (Van- Moll., p. 125, t. 13, f. 2. Tr. 

 quadr telnet us S. WOOD, olim. Zizyjihiiius alabastrum Beck, REEVE 

 Conch. Icon., f. 46. T. occidentalis Migh., SARS, Moll. Reg. Arct. 

 Norv., p. 142, t. 9, f. 7, t. iv, f. 5 (dentition). 



An exquisite little gem, like an opal in its iridescence, with smooth, 

 narrow, more opaque riblets. It has the same distribution as several 

 species of Margarita. 



(Group of C. exfifijtcratum Pennant.) 

 C. EX Asi'EUATUM Pennant. PI. 17, figs. 20, 42 ; pi. 18, figs. 5-8. 



Shell small, turreted, solid, thick ; color purplish-brown, blackish- 

 purple or red, with white longitudinal lines or stripes, the base 

 radiately striped or dotted with white. Surface lusterless, the whorls 

 encircled at the peripheral carina by a rounded granulate ridge, 

 above this with 4 spiral granose line, the interstices densely, 

 regularly marked by elevated lamellar stria? ; base encircled by 6 

 concentric lira?, narrower than the densely radiately striate inter- 

 stices ; apical whorls red. Spire very high; whorls 9-10, the last 

 angular, aperture quadrangular, throat brilliantly iridescent, basal 

 margin thickened, columella subvertical, obliquely truncate below. 



Alt. 12, diam. 62 mill.; alt. 10, diam. 6-1 mill. 



Mediterranean, Adriatic and Black Seas ; Atlantic Ocean, England 

 and Belgium to Canaries; Madeira and Azores Is. 



T. exasperatus PENNANT, Brit. Zool. iv, p. 126 (1777). JEFFREYS, 

 Brit. Conch, iii, p. 324; v, p. 203, t. 63, f. 4. FISCHER, Coq. Viv., 

 p. 266, t. 89, f. 1. B., D. & D., Moll, du Rouss., p. 362, t. 43, f. 1- 

 7. And of other authors. T. conulus DACOSTA, Brit. Conch., p. 40, 

 t. 2, f. 4. T. minutus, striatus, etc., CHEMNITZ, Conchyl. Cab., v, p. 

 30, t. 1529. T. minutus Chem. DESHAYES, in Lam., An. s. Vert, ix, 

 p. 151. T. erythroleucos GMEL., Syst. Nat. xiii, p. 3581. LAM., 

 An. s. Vert, vii, p. 30. T. exiguus PuLT.,Cat. Dorset., p. 48, t. 12, 



