Hikidea osoensis sp. nov.

(Fig. 3 E–I)

Diagnosis. Shell turbiniform, continuously convex and weakly inflated with weakly expressed concave ramp at the adapical suture. Surface smooth apart from some weak and hardly recognizable spirals and strongly prosocline growth lines.

Holotype: GZG.INV.84968, height H = 10.7 mm, width W = 9.6 mm.

Paratype: GZG.INV.84969, H = 8.8 mm, W = 7.0 mm.

Type locality and strata: Bear Creek, Colusa County, California, USA; locality # 4 in Kiel et al. (2008b). Great Valley Group, Grizzly Canyon member of Crack Canyon Formation; Valanginian (Early Cretaceous).

Other material: Five additional specimens from the type locality including a juvenile shell (GZG.INV.84970) illustrated in Fig. 3 I.

Description. Protoconch unknown. Shell turbiniform with four whorls, convex with no angulations. Concave ramp at the adapical suture weakly expressed. Juvenile shell ornamented by numerous spiral ribs. Adult shell surface smooth apart from some weak and hardly recognizable spirals and strongly prosocline growth lines. Generating curve circular, aperture tangential, peristome uninterrupted. Inner lip with narrow callus, outer lip not preserved. No umbilicus.

Remarks. Hikidea osoensis differs from H. omagariensis and H. yasukawensis by its much larger size and higher shell with more numerous whorls. The Recent Cantrainea nuda is also smaller and has a slightly angulated demarcation between the flank and the base, and less convex whorl flanks. This occurrence is the earliest known record of the genus.

Distribution. Type locality only.

Etymology. From Oso, Spanish for bear, referring to the name of type locality.