398 BRITISH PALAZOZOIC FOSSILS. [GasrErRopopa. 
5th Class) GASTEROPODA. See page 288. 
6th Ord. PECTINIBRANCHIATA. See page 289. 
14th Family. HALIOTIDA. See page 290. 
Genus. PLEUROTOMARIA. See page 291. 
PLEUROTOMARIA IMBRICATA (/t6me7). 
Ref—Harzgebirge, t. 8. f. 1. 
Sp. Ch.—Obtusely conical ; apical angle 95°; of four and half whorls, those of the spire rounded, or very 
obtusely subcarinate, from the projection of the broad square band, placed rather nearer the lower than the 
upper suture, and the lower margin of which is most prominent; body-whorl subquadrate from the upper third 
between the suture and the band, being obliquely. and rather strongly flattened, the middle third below the band 
being nearly parallel with the axis, and the lower third rather abruptly sloping inwards; one or two spiral 
strie on the keel, the whole surface marked with similar thread-like spiral ridges, separated by rather more 
than their thickness, and irregularly subalternate in size, crossed by very fine, slightly oblique lines of growth, 
about eight or nine spiral strive on the keel, above the body-whorl. Length nearly eleven lines, proportional 
length of body whorl ;*,, length of penultimate whorl ;;, width ;j. 
T believe there is no umbilicus, but am not quite sure of the fact. 
Position and Locality—Not uncommon in the Devonian limestone of Newton Bushel. 
PLEUROTOMARIA INTERSTRIALIS (Phill.) 
Ref. and Syn.—Phill. Geol. York. Vol. IL. t. 15. f. 10 = Pleurotomaria aspera Sow. Geol. Trans. 2nd Series, 
Vol. V. t. 54. f. 16. 
Sp. Ch.—Obtusely conical; apical angle about 95°, sometimes a little higher or lower, spire of five 
obtusely angulated, gently convex whorls; keel strong, thick, prominent, usually marked by four or five very 
fine spiral strize, but sometimes simple ; usually about five, strong, regular, spiral, thread-like striz above the 
keel on the body-whorl, with a very minute one between each pair (but only three on the whorls of the spire, 
the middle one most prominent), the whole crossed by more regular, nearly equal, slightly oblique elevated lines, 
(meeting the keel at 65°) nearly twice their thickness apart (four in the space of one line on the body-whorl), 
which form spinulose tubercles at their intersection with the spiral ridges ; surface beneath the keel marked in 
the way as above it, the keel being also similarly reticulated ; umbilicus small, rounded, diameter about seven 
lines, proportional length =, length of body-whorl =, diameter of umbilicus *. 
There is considerable irregularity in the ridging of this fossil, but there is no doubt, I think, of the pro- 
priety of uniting Mr Sowerby’s and Mr Phillips's species. 
Position and Locality—Very common in the slate of S. Petherwin. 
19th Family. PYRAMIDELLIDA. See page 302. 
Genus. MACROCHILUS (Phill.) 
Ref—Pal. Foss. 
Gen. Char.—Shell short, ovate, gibbous; spire rather short, pointed, of several convex whorls ; body-whorl 
large ; aperture broad, ovate, rounded in front, pointed behind, indented by the preceding whorl ; outer lip thin, 
