^40 Dr Fleming on the British Testaceous Annelides. 
4. Z>. Gac?ws.~Hake’s Tooth — Body of the shell contracted towards the 
mouth. Mont. Test. Brit. p. 496. tab. xiv. fig. 7* Common in the British 
Channel, adhering to the sounding-line, Montagu. 
The length is about |ths of an inch. Diameter, where thickest, f gth. The 
shell is white, subpellucid, glossy, and tapers to a fine point. 
B.' Extinct Species. 
a. Shell furnished with longitudinal striae or ridges. 
5. D. striatum — Shell with 10 or 11 acute, prominent striae, and several 
obsolete intermediate ones. Sowerby’s Mineral Conchology, tab. Ixx. fig. 4. 
Hordwell and Barton Cliffs, Mrs Tylee and Rev. Mr Bingley. 
The striae are less distinct and prominent towards the mouth. The inter- 
vening striae, from 1 to 4, are most obvious near the middle of the shell. 
The fines of growth are numerous and fine. The aperture is circular. 
6. D. decussatum — Shell with about 20 striae, and intermediate obscure ones. 
Sower. Min. Conch, ib. fig. Sussex, William Borrer, Esq. 
The fines of growth are numerous, distinct and oblique. The mouth is 
elliptical. 
7. D.costatum — Shell with about 12blosely set ridges. Sower. Min. Conch, 
ib. fig. 8. Holywell Craig, Mrs Cobbold. 
The ridges and grooves are nearly equal and rounded. The fines of growth 
are obscure. The aperture is circular. 
8. D. septangulare. — Shell with 7 rounded ridges and grooves. Plate IX. 
Fig. 1. Belfast. 
I found this species at Colin Glen in the bed beneath the chalk, and which 
probably corresponds with the Green-sand Formation of England. It is 
about |ths of an inch in length, and scarcely y^th in diameter at the 
aperture. The shell is very thick, and has a considerable curvature. 
The marly sandstone in which it was imbedded, filled the cavity of some 
individuals, while others contained a cast of crystalline carbonate of lime, 
mixed with iron-pyrites. The shell itself was changed into a substance 
resembling in its texture the conchoidal varieties of the older chalk. 
b. Shell destitute of longitudinal markings. 
9. Z>. nitens. — “ Nearly straight ; surface even and shining, aperture circu- 
lar; mouth expanded.” Sower. Min. Conch. Ixx. fig. 1. 2. Highgate clay, Mr 
Sowerby. 
The shell tapers gradually to the smaller end, where it is thickest. It 
reaches an inch and a half in length. 
10. D. entaloides “ Slightly arched, surface waved, nearly smooth ; edge 
of the mouth acute ; apertures smooth.” D. entails ? Sower. Min. Conch, ib. 
fig. 3. Hordwell Cliffs, and Stubbington, Mr Sowerby. 
Mr Sowerby entertained some doubt whether this was a fossil shell, or dif- 
ferent from our 3d species ; but his subsequent addition of the second 
habitat intimated that these had been removed. 
1 1. Z). ellipticum — Nearly straight, quickly tapering, rather compressed, 
surface uneven, aperture circular ; external edge elliptical.” Sower. Min. 
Conch, ib. fig. 6, 7* Folkstone, Kent, Mr Gibbs. 
“ The shell being thicker along two sides, gives the tube a depressed form, 
and makes the outer margin of the mouth elliptic ; the fines of growth 
give the surface a rugged aspect ; internally it is beautifully pofished : 
the diameter of the mouth is sometimes nearly half an inch.” 
1 2. D. planum “ Gently tapering and curving, smooth ; aperture round ; 
lip a little thickened, sharp-edged.” Sower. Min. Conch, tab. Ixxix. fig. 1. 
In greenish sandy limestone, Bognor, Mr Boys. 
This species, the shell of which is nearly an inch in length, appears to have 
been gregarious. 
