Retidrillia megalacme

Retidrillia megalacme is a species of sea snail, a marine gastropod mollusk in the family Borsoniidae.^[1]

Retidrillia megalacme
Original drawing with an apertural view and the protoconch of a shell of Retidrillia megalacme
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
Subclass:	Caenogastropoda
Order:	Neogastropoda
Superfamily:	Conoidea
Family:	Borsoniidae
Genus:	Retidrillia
Species:	R. megalacme
Binomial name
Retidrillia megalacme (Sykes, 1906)
Synonyms[1]
Drilliola megalacme (Sykes, 1906) Spirotropis megalacme Sykes, 1906 (original combination)

Description

The length of the shell attains 5 mm, its width 2.5 mm.

(Original description) The small shell has a conical-fusiform shape. The spire is well raised and fairly solid. Its colour (dead) is whitish-brown, with a white protoconch. It contains 6. turreted whorls, regularly increasing. The white protoconch is large. The first whorl and a half are smooth, then closely set longitudinal riblets are seen, and the whorl becomes carinate. The remaining whorls are acutely carinate, with an area below the suture, either smooth or with arcuate striae. Below the carina appear numerous longitudinal riblets, decussated by spiral carinations, giving the shell a somewhat prickly or nodulous appearance. The aperture is small, with a well-marked sinuation above. The columella is vertical, a little twisted at the base.^[2]

Distribution

This species occurs in the Atlantic Ocean off Portugal.