396 GASTROPODA. [Pectinibranckta. 



Shell ovate, ventricose, body-whorl variously sculptured ; aper- 

 ture ovate, contracted below, but without a canal, and deeply notched, 

 with a high fasciole ; outer lip crenulated internally ; columella 

 smooth, carinated, and twisted by an obliquely transversal plait ; 

 inner lip often widely spread over with enamel, with a callosity or 

 blunt dentiform plait on the parietal wall. Margin of operculum 

 entire or serrated. 



Distribution. World-wide, principally in the waters of tropical 

 and subtropical latitudes. 



Fossil in the Tertiary ; the maximum in the Miocene. 



KEY TO SPECIES. 



n. Body-whorl with 5-6 spiral rows of tubercles . . . . dissintilis. 



//. Body-whorl with 5-6 spiral rows of sharp prickles . . ephamilla. 



c. Body-whorl with 9 spiral ribs, crossed by about 20 axial ribs, 



crossing-points granular . . . . . . . . fasciaia. 



d. Whorls with a narrow shoulder coronated with a row of 



tubercles of the axial ribs . . . . . . sutiinil!* j>m/ker>. 



1. Alectrion dissimilis, Watson, 1886. Plate 19. fig. 1. 



Nassa dissimilis, Wats., Chall. Rep., xv, 1886, 175, pi. 17, f. 6. 



Shell thin, very stumpy, with a short broad body-whorl, short 

 rounded base, short conical subscalar spire ; a very short, gibbously 

 rounded aperture, and an excessively short columella. Sculpture : 

 There are frequent feeble riblets at irregular distances, which are 

 dotted with small round tubercles ; the shallow parting furrows are 

 broadish, and are scored with strongish lines of growth. Spirals the 

 tubercles on the riblets, though unconnected, are yet arranged in 

 rows, of which there are 5 or 6 on the body-whorl ; below these, on 

 the base, are 5 feeble distant threads. Colour white. Spire low and 

 stumpy, subscalar, height about that of the aperture. There are 4| 

 whorls remaining (apex broken) ; they are short, broad, and convex, 

 the last a little tumid, with a short rounded base. Aperture direct, 

 small, round, not channelled above, deeply notched at the base. Outer lip 

 regularly curved. Columella very short. Inner lip flat across the body. 

 advancing very little. Fasciole distinct, the upper edge with a sharp 

 thread, above which lies a furrow. Operculum unknown. (Watson.) 



Diameter, 9-25 mm. ; height, 14 mm. 



Animal unknown. 



Type in the British Museum. 



Hnb. Chall. Stat. 168, east of Blackhead, in 1,100 fathoms. 



2. Alectrion ephamilla, Watson, 1882. Plate 19, fig. 2. 



Nassa (Trilia) ephamilla, Wats., J.L.S., xvi, 1882, 370; Chail. Rep., xv, 

 187, pi. 11, f. H ; Button, T.N.Z.I., xvi, 233 ; Index, 72. 



Shell rather small, thin, chalky porcellanous, ovate, with a shortish 

 scalar spire, a rounded apex, a marginated suture, whorls rounded 



