300 BRITISH PALAOZOIC FOSSILS. : [GAsTEROPODA. 
Position and Locality—Common in the Bala slates of Cyrn-y-Brain, Wrexham, Denbighshire, and in 
the schists of Goldengrove, Llandeilo, Caermarthenshire. 
Explanation of Figures.—P\. 1. K. fig. 37, natural size, from schists of Cyrn-y-Brain; fig. 38, small 
specimen, seen from below. 
Genus. MACLUREIA (Leseur). 
Gen. Char.—Discoid, sinistral, of numerous exposed whorls, flattened above, rounded below; mouth usually 
longer than wide, spire flattened ; surface smooth, or marked only by transverse lines of growth. 
This genus differs from Straparollus or Huomphalus by being reversed and having a large shelly oper- 
culum, with a strong articulating tooth nearly as in Nerita ; the species are at present only known in the 
lower Cambrian deposits of America and Scotland. 
MACLUREIA MACROMPHALA (M‘Coy). Pl. 1. L. fig. 12. 
Sp. Ch.—Discoid, sinistral, usually elliptical, of about three and a half rapidly enlarging whorls; spire 
depressed below the level of the outer turn, which bears an obscure, obtusely rounded angulation, bounding the 
slightly oblique upper plane of the shell; circumference obtusely rounded; under side having the middle of the 
whorls obtusely angulated, thus defining a wide, shallow umbilicus. Diameter ten lines, proportional diameter 
of last whorl =, height of last whorl *, diameter of umbilicus "%. Surface crossed by minute, thread-like 
lines of growth, extending obliquely backwards from the suture, and then crossing almost directly into the 
umbilicus. 
This little species is easily distinguished from the JZ. magna by its very wide umbilicus (resembling that 
of the carboniferous Huomphalus pentangulatus), and by the more rapidly enlarging whorls, which also sepa- 
rate it from the imperfectly-known M7. matutina and M. sordida (Hall), from the calciferous sandstone of New 
York. 
Position and Locality—In the cencretionary and schistose limestone of Craig Head, near Girvan, 
Ayrshire. 
Explanation of Figures —P\.1. L. fig. 12, natural size, viewed from above; fig. 12a, viewed from 
below. 
MACLUREIA MAGNA (Leseur). PI. 1.L. fig. 13. 
Ref—Leseur, Journ. Acad. Nat. Sci. Philad. Vol. I. p. 312. t. 13. f. 1, 2, 3. Hall, Pal. New York, t. 5. f. 1. 
Sp. Ch.—Sinistral, discoid, spire scarcely elevated, of four to five gradually increasing whorls, flattened 
above, with an obtusely rounded angle at the circumference, giving a depressed appearance to the sutures, and 
from which the slightly convex base of the last whorl slopes rapidly to the angular edge of the deep umbilicus, 
which partially exposes the whorls; mouth obtusely trigonal; surface crossed by fine imbricating lines of 
growth. Diameter three and a half inches, proportional height of last turn =, width of last turn ¥, width of 
umbilicus 2. 
I was greatly delighted, on Prof. Sedgwick bringing me a parcel of the unpromising-looking metamorphic 
concretionary, calcareous schists of Knockdollian Quarry, to recognize, for the first time in Europe, a number of 
specimens of this important fossil, so remarkable in America for its great geographical, and exceedingly small 
geological range; being confined to the chazy limestone (nearly at the base of the lower Paleozoic group of 
the United States), in which it abounds, and, according to Hall, characterising this bed from North-east of 
New York to Kentucky and Tennessee, and North-westerly nearly to Lake Superior. It is therefore of great 
interest to find this fossil in Britain, and to know, from the analogy of the New York section, that we are close 
to the first appearance of organised beings. As doubts have been thrown on my identification of the Scotch 
with the American species, I have thought it necessary to give figures of the former, demonstrating their pre- 
cise accordance in all respects with the figures of Hall. 
