JOURNAL OF CONCHOLOGY. Bie 
ADEORBIS UNISULCATUS, NEW SPECIES, 
FROM THE IRISH ‘COAST. 
By GEO. W. CHASTER. 
(Read before the Conchological Society, November x1th, 1896). 
Adeorbis unisulcatus n.sp. 
Shell much depressed, thin, colourless, nearly transparent, 
composed of about two whorls; sculpture consisting of 
very numerous spiral rows of minute punctures, more or 
less obscured by the closely-set, oblique, raised, lines 
which cover the surface; below the periphery there is 
a deep spiral groove formed by an infolding of the shell 
substance, a slight and shallow groove also surrounds the 
umbilicus ; whorls rounded above and rather sharply 
angulated at the base ; nucleus smooth and somewhat 
obliquely placed; suture deep and channelled ; umbilicus 
very large, exposing the internal spire; mouth quad- 
rangular, very oblique; outer lip retreating above and 
below, deeply notched by the spiral groove. 
Height 0-4 mm., Diam. 08 mm. 
This species has much the appearance of A. zmperspicuus 
Monts., when viewed as it usually is from 
above or below. The two are, moreover, 
frequently associated. From that species it 
is distinguished by its invariably smaller size, its more out- 
spread manner of growth, and especially by the remarkably 
deep spiral groove. When I noticed the differences and 
proceeded to separate my specimens of the two species (about 
one hundred in number) from various localities, I was sur- 
prised to find that although 4. cmperspficuus varies consider- 
ably, the present form is constant in its characters and very 
distinct from any variety of the other. 
Two dead specimens were dredged off Rue Point, Rathlin 
Island, in seventeen fathoms. I have it also from Oban, 
Roundstone, Plymouth (where it is not very rare), and Tangier. 
A single dead shell of 4. cmperspicuus was found in the same 
material from off Rathlin Island. 
