Mitrell<i.] GASTROPODA. 431 



(Jen us 1. MITRELLA (Risso, 1826), Morch, 1859. 



Mitrdla, Risso, Hist. Nat. Europe Merid. iv, 247. No type- specified. 

 Mitrella, Morch, 1859. Type : Mure.x wriptus, Linne. Anr/ulatomitreUa 

 and Arcuatomitretta, Sacco, 1889. 



Shell small, narrowly elongated ; spire high, acute, smooth, conical ; 

 protoconch paucispiral, nucleus obtuse ; whorls almost flat and the 

 suture linear ; the last whorl not ventricose, oval, attenuated below 

 and but little contracted, sometimes with a few spiral grooves ou the 

 short neck ; aperture small, the margins not parallel, the height not 

 more than the total height of the shell, lightly channelled above, 

 without a canal below, truncated and moderately notched ; outer lip 

 nearly vertical, not varicose, crenate inside, not thickened in the 

 middle ; columella straight, smooth, slightly twisted below ; inner 

 lip but little callous, sometimes with a few unequal ridges. Open-alum 

 horny. 



Distribution. Mediterranean, Antilles. Pacific Ocean, &c. 



Fossil in the Tertiary. 



KEY TO SPECIES. 



A. Height of spire about the same as that of the aperture. 



a. Surface smooth, a few spirals at the base. 



1). Body-whorl moderately convex ; outer lip often 



crenate within . . . . . . . . choava. 



bb. Body- whorl ventricose ; outer lip smooth within stephanophora. 

 aa. Surface with faint microscopic spiral lines ; suture 



false- margined . . . . . . . . leptalcn. 



and. Surface with spiral cords, interstices linear ; suture 



simple . . . . . . . . . . \Yvbsteri. 



B. Height of spire about 1| times that of the aperture. 



a. Surface smooth, a few spirals at the base. 



6. Spire-whorls flat ; outer lip denticulate ; suture 



false-margined . . . . . . . . pseudomarijinata. 



bb. Spire-whols convex ; outer lip smooth ; suture 



linear . . . . . . . . . . rosea. 



aa. Surface with a few microscopic spiral lines and a few 

 varices ; body-whorl angled . . . . . . 



aaa. Surface with dense microscopic spiral lines, decus- 

 sated by growth-lines ; body- whorl convex .. subantarcti'a. 



1. Mitrella choava, Reeve, 1859. Plate 19, fig. 13. 



Columbella choava, Rve., Conch. Icon., xi, pi. 37, f. 239; Crit. List, 22; 

 M.N.Z.M., 61; T.N.Z.L, xvi, 223; Man. Conch. (1), v, 137, pi. 51, 

 f. 51. Pyrene flexuosa, Button, J. de Conch., 1878. 23 ; T.N.Z.L, x, 

 295; Murdoch, T.N.Z.L, xxxvii, 225. P. chotiva. Reeve: Iredale. 

 T.N.Z.L, xl, 385. 



tihell very small, elongated, smooth, fulvous or dark brown with 

 variable colour-markings. Sculpture consisting of a few spiral ridges 

 on the lower part of the base only ; growth-lines very fine and almost 

 straight. Colour very variable : a, dark brown without any mark- 

 ings ; b, dark brown with a pale band below the periphery of the 

 bodv-whorl ; c, dark brown with a light band below the suture on 



