Verticosta robusta Huang & Lin 2020, n. sp.

Verticosta robusta n. sp. 縱肋毛螺 (Plate 1, fig. 4) DESCRIPTION

Shell up to 12.7 mm, large for genus, high-conic and turriform, solid and coarse in surface. The whorl edge is gently inflated on the upper 3 whorls and more inflated on the lower whorls. Suture is deep and distinct. Aperture length is 38% of shell length and body whorl length is 64% of shell length. Protoconch of 1.75 smooth and inclined whorls while the lower whorl is wide than the upper whorl. Teleoconch of 5.25 whorl is ornamented with strongly elevated and evenly spaced axial ribs; 12 ribs on the 1 st and 2 nd teleoconch whorls, 14 ribs on the 3 rd and 4 th teleoconch whorls and 10 ribs on the body whorl. The ribs on the 1 st teleoconch are vertical and the ribs on the lower whorls become more and more prosocline. 3 primary cords develop on the 1 st teleoconch whorl and these cords retain their number and strength till the body whorl. Infrasutural adapical primary cord appears immediately on the 1 st teleoconch whorl and develops 2 secondary cords on the 2 nd teleoconch whorl then successively develops 4 tertiary cords on the 3 rd to 4 th teleoconch whorls. The edge of infrasutural adapical cord derived cord surface is straight and the edge of P1 to P3 derived cord surface is inflated, thus making an angulated shoulder overriding P1. There is 10 spiral cords on the body whorl. These spiral cords are of one third strength of the axial ribs and pointed nodules are noted at the transections of axial and spiral sculptures. The interspaces are horizontally elongated, deep and concave and accommodate numerous microscopic axial threads. Shell base somewhat attenuated in front, smooth and concave; aperture rounded and recessive on inferior margin. The columellar process is smooth and straight with a callus over the superior junction with the concave shell base. The outer lip is thin and crenulated on cord terminations. The medial lip is well defined and continuous with a short and narrow umbilical chink. Ground color is fawn on the spire and upper two third of the body whorl and ivory white over the lower third of the body whorl and cord surface of axial ribs. Periostracum absent; operculum unknown.

Holotype: shell height 12.69 mm x width 8.53 mm, Taiwan, Keelung, 250 m depth. NMNS-8152 -001.

Taiwan, Keelung, 25 0 m depth.

Currently restricted to type locality, East China Sea, Taiwan, Keelung, 2 5 0 m depth; fine gravel bottom.

This new species is distinct from Verticosta migrans (Dall, 1881) n. comb. by an angulated configuration in ribs. The strength of axial ribs and spiral cords in V. robusta n. sp. is strong than that in the comparable parts in V. migrans n. comb..

This new species is the robust one in this group.