550 BRITISH PALAZOZOIC FOSSILS. [GasTEROPoDA. 
7th Ord. DENTALINA. 
This order contains but one family, Dentalidw, of one Genus, Dentalium. 
Genus. DENTALIUM (Zinn.) 
Gen. Chavr.—Shell tubular, elongate conic, arched, open at both ends; usually a dorsal slit at the smaller 
end, and often two lateral retractor muscular impressions ; aperture round, simple. (Animal conic, head distinct, 
lips with tentacles, gills in two symmetrical bunches, one each side of the neck; anus at the smaller end; foot 
proboscidiform, with a shelly appendage at the end.) 
Allied by the shell to a greatly elongate Pissurella. 
Recent on sandy and rocky bottoms in all latitudes, particularly warm ones. 
DENTALIOM DENTALOIDEUM (Phill. Sp.) 
Ref. and Syn.= Orthoceras dentaloideum Phill. Geol. York. Vol. II. t. 21. f. 12. = Dentalium ornatum de Kon. 
Anim. Foss. Bel. t. 22. f. 3. 
Desce.—Very elongate, conic, gently arched, section almost circular, very faintly compressed ; shell very 
thick except at the anterior edge ; surface sculptured with very small, sharp, prominent, subequal, longitudinal, 
thread-like ridges (eight in one line at three lines in diameter), crossed by slightly oblique lines of growth of 
variable strength. Casts are generally smooth, abruptly dilated towards the anterior end, and marked with a 
longitudinal groove down the dorsal and another down the ventral aspect, commonly bounded by two obscure 
ridges, but sometimes prominent in the middle, or even triple; very faint traces of longitudinal strize towards the 
smaller end. Length of average specimen, imperfect at the smaller end, three inches; diameter at anterior end 
six lines, diameter at smaller end two and a half lines, thickness of shell at smaller end one line. 
M. de Koninck mentions haying found the small end covered in great part by a diaphragm having a slit 
from its middle to the dorsal edge; I have not seen this most curious character. The transverse striz, according 
to Baron de Ryckholt, are in some specimens as strong or even stronger than the longitudinal ones, producing a 
reticulated surface. Owing to the closely sculptured surface adhering to the matrix, specimens usually shew only 
the internal casts. 
Position and Locality—V ery common in the carboniferous limestone of Lowick, Northumberland. 
DENTALIUM INGENS (de Kon.) 
Ref.—de Kon, Anim. Foss. Bel. t. 22. f. 2. 
Desc.—Hlongate, conic, very gradually tapering, gently arched; section with a scarcely perceptible ellip- 
ticity; shell extremely thick, coarsely laminated concentrically ; surface with coarse, irregularly imbricating 
transyerse lines of growth. A specimen (imperfect at each end) six inches and nine lines long, is one inch 
and half a line in diameter at the larger end, and four and a half lines in diameter at the smaller end, where 
the thickness of the shell is one and a half lines, and the diameter of the internal cavity about two lines; the 
thickness of the shell at the larger end is two lines on the inner side of the curve, and one and a half lines 
on the convex side. 
M. de Koninck states that the small end is simple, and that the anterior aperture is oblique, as well 
as the concentric imbricating strive. I believe it is so in our specimen, but I cannot see all parts of it. By 
the help of Mr Carter I submitted a fragment, prepared as a transparent microscopic object, to a high magni- 
fying power, doubting that this gigantic species could be a real Dentaliwm, but the intimate structure proved 
perfectly analogous to that of the living small Dentalia. 
Position and Locality.—Rare in the carboniferous limestone of Kendal, Westmoreland. 
