198 GIBBULA. 



T. magus Linne., Syst. Nat, xii, p. 1228 (1766). — Philippi, 

 Conchijl. Cab., p. 18, t. 4, f. 1, 2.— Forbes & Hanley, Brit. 

 Moll., t. 65, f. 6, 7. — Jeffreys, British Conch., iii, p. 305, t. 52, f. 1- 

 — Hidalgo, Mol. Mar. de Esp., t. 58, f. 3-6. — Fischer, Coq. Viv., 

 p. 110, t. 6b, f. 1. — BuQ. Dautz. et Dollfus, MoV. Mar. Rouss., p. 

 373, t. 44, f. 1-11. — T. tuberculatus Da Costa, Brit. Conch., p. 44, t. 

 3, f. 1, 2.— T. viajus SdwB., Ill Ind. Brit. Sh., t. ll,f. 19.— T. hicar- 

 inatus Gray, in Griffith's Cuvier's Anim. Kingd., t. 1, f. l.= T. gray- 

 anus Phil., Conchyl. Cab., p. 281, t. 41, f. 6. 



An abundant species. There is great variation in color. A 

 small white or cream colored variety is found on the Mediterranean 

 coast of France. 



The natural position of G. magus is between the group known as 

 Forsktilia (G. declivis, fanula, guttadauri, fanuloides) and the G. 

 albida L. It is equally rehited to both the former and the last-named 

 species, but being the type of the genus I have given it first place. 

 The Mediterranean Gibbula, although they have been divided into 

 numerous " subgenera," form a quite homogeneous grou]i, in which 

 species succeeds species so closely that only careful analysis enables 

 us to discriminate them. Only in one place can I see a hiatus of super- 

 specific value in the series ; and that break, indicated by asterisks 

 on p. 204, separates the species having acuminate, acute spires from 

 those in which the outlines of the spire are more convex, not atten- 

 uated toward the apex. For the latter group the name Phorcus of 

 Risso may be retained by those who can see any use in such trivial 

 distinctions. 



G. DECLIVIS Forskiil. PI. 31, figs. 47, 48. 



Shell umbilicate, conical, solid, whitish, maculated with purplish 

 or yellowish ; whorls about 6, bicarinate at the periphery, all over 

 spirally Urate, the upper surhice strongly radiately costate, the folds 

 terminating at the periphery in short spines ; periphery encircled by 

 a channel bearing a median riblet ; base convex, bearing 4 or 5 

 strong concentric lirpe ; aperture rounded, smooth within ; columella 

 sinuous, arcuate, dentate at the base ; umbilicus moderate, deep. 



Alt. 20-24, diam. 22-27 mill. 



Red Sea; Gulf of Akaba. 



Turbo declivis Forskal, Descrip. animal., p. 126. — Savigny, 

 3foll. de I' Egypt, t. 3, f. 1, 'l.^Trochus declivis Philippi, Conchyl. 



