GASTEROPODA OF THE LOWER GREEN MARLS. 155 
Subclass OPISTHOBRANCHIATA. 
Order TECTIBRANCHIATA. 
TORNATELLIDZ. 
Genus AcT&ON Montf. (=Tornatella Lam.) 
ACTON SUBOVOIDES, n. sp. 
Plate x1x, Figs 14-16. 
Shell longitudinally subovate, with a very short, obtuse spire; num- 
ber of volutions undeterminable from the imperfection of the specimen; 
body volution gently convex and constituting the greater bulk of the speci- 
men; aperture elongate elliptical, fully three times as long as wide, rounded 
below and acute above, measuring about four-fifths as long as the body 
volution, taken on the same side as the aperture; columella, as seen in the 
casts, apparently marked by two folds, both of which are rather obscure 
and seen only as slight impressions on the surface of the columellar cavity, 
and quite high, so as to be invisible in a drawing of the aperture; surface 
marked by rather fine, spiral lines, coarser on the lower part than above, 
and the surface of the cast marked by a rather broad depressed spiral band 
or groove, a little below the suture. Indications of transverse lines of 
growth are extremely faint. 
This species approaches most nearly to A. Forbesi, but differs in the 
general form, being more oval and less heavy below, and in the upward 
length of the aperture, which is not nearly so high as in that one. It also 
differs very materially in the form and position of the fold of the columella, 
which will be readily seen on comparing the figures. 
Formation and locality: The specimen came to me from the Acad. Nat. 
Sei., Phila., where it was found with an old label indicating it as a type of 
A. ovoides Gabb, and at first was used under that title, although differing 
very materially in proportion from the measurements given by Mr. Gabb. 
Subsequently the true type of that species was discovered with the author's 
own label, and was found to be very distinct from this one, and is an 
Avelana, consequently leaving this to be classed as a new species. The 
