GASTEROPODA. | LOWER PALAOZOIC MOLLUSCA. 295 
part of each whorl, is indicated by Mr Sowerby in his figure or description (in the Sil. Syst.) of the 
P. Corallii, 1 suppose the present species to be distinct. 
Position and Locality—Common in the Upper Ludlow of Spital, and Benson Knot, Kendal, West- 
moreland ; tilestone of Storm Hill, Llandeilo, Caermarthenshire. 
Explanation of Figures —P1|. 1. L. fig. 19, from the Upper Ludlow rock, near Kendal, natural size ; 
fig. 19 a, two whorls magnified. 
15th Family. TROCHID. 
Shell of several spiral, gradually increasing whorls, conic or depressed ; aperture small, more or less rounded, 
without notch, nacreous within: (animal of moderate size, foot triangular, with long filaments from its upper 
part, distinguishing it from all other gasteropods; head with two tentacles, having the eyes on pedicles at 
their base; sexes separate; operculate). 
Genera :—1, Turbo; 2, Trochus; 3, Phorus; 4, Pitonellus; 5, Solarium; 6, Straparollus ; 7, Euompha- 
lus; 8, Maclureia; 9, Eccyliomphalus; 10, Delphinula ; 11, Phasianella. 
Genus. TURBO (ZLinn.) restricted. 
Gen. Char.—Shell thick, of moderate or large size, ovate; body whorl rounded, ventricose ; spire rather 
small, of several convex whorls, pointed; surface often spirally grooved or nodulated; aperture large, nearly 
circular, slightly produced and broadly rounded in front, more or less modified by the preceding whorl; outer 
and inner lips thin; operculum thick, shelly, rugged without ; flattened, and spirally suleated within ; with or 
without an umbilicus. 
These shells are larger than the Litorinw, and are distinguished from those by their mouth being more 
dilated in front, nacreous within, and the columella not being flattened, as well as by their thick stony 
operculum ; which latter, as well as the ventricose rounding of the base of the body whorl and circular mouth, 
distinguish them from Trochus. 
Recent, herbivorous, a little below low-water mark in warm seas, and in all intermediate marine periods, 
from the Cambrian. 
TURBO CREBRISTRIA (A/°Coy). Pl. 1. K. fig. 36, and Pl. 1. L. fig. 22. 
Ref—Ild. M°Coy, Ann. Nat. Hist. 2nd Series, Vol. VII. p. 49. 
Sp. Ch.—Ovate, of four very rapidly enlarging volutions; spire small; apical angle about 85 or 90°: 
whorls convex, with an obtusely bounded narrow concave space at the sutures above; back broad, gently convex ; 
umbilicus narrow, deep, effuse at the edge, mouth very large, obscurely angulated retrally ; shell thick, surface 
girt with sharp, spiral, thread-like ridges, nearly twice their thickness apart, about four in the space of one line 
on the penultimate whorl, with an occasional finer one between a regular pair, on the last whorl of old 
specimens, the 2nd, 3rd, 4th, or 5th, are irregularly larger, all crossed obliquely by very fine, regular, sharp 
lines of growth, eight in one line. Length (of small perfect specimen) one inch, proportional width 3%, length 
of body whorl 4 (grows to nearly two inches in diameter). 
The large casts of this species are smooth, and resemble Sowerby’s figure and description of 7. Prycew, 
except that the beak is broad, and rather flattened, or slightly convex, instead of being angular in the middle, 
as that species is defined to be. ‘The substance of the shell is thick, and its mode of striation resembles that 
of the so-called Plewrotomaria bilix of Conrad, as figured by Hall (Paleontology of New York), which is 
however distinguished by its smaller size, longer spire, and want of an umbilicus. 
Position and Locality—Common of large size in the calcareous Bala schists of Gelli Grin, Bala, Merio- 
nethshire; in the fine sandy schists of Mandinam, Caermarthenshire; in the fine Bala sandstone of Alt yr 
Anker, Meifod, Montgomeryshire ; in the Bala limestone of Mynydd Fron Frys, five miles W. of Chirk, Den- 
bighshire. 
Explanation of Figure —P1\. 1. K. fig. 86, small specimen, natural size. 
