288 BRITISH PALAZOZOIC FOSSILS. [Preropopa. 
of one line in the middle of the shell (where the diameter of each face is about six lines), rather abruptly 
increasing to six or seven near the smaller and larger ends; intervening shallow spaces marked with coarse 
longitudinal strize; average length about two and quarter inches. 
In this species I frequently observe the longitudinal furrow at the upward angle of the plicze to be absent, 
sometimes absent and present in different parts of the same specimen; the difference of size and closeness 
above noticed is also taken from the examination of several specimens, each exhibiting the change. The 
specimens vary in the amount of depression, and consequently in the angle at which the sides converge ; 
which therefore is of far less value as a specific character than the angle which the two sides of each face 
make with each other, care of course being taken that in the given species the faces be equal in width, or 
else their angles be separately given. 
Position and Locality—Common in the Upper Ludlow rock of Benson Knot, Kendal, Westmoreland ; 
common in the Asterias bed of Underbarrow, Kendal, Westmoreland ; in the fine gritty beds upon the Bala 
limestone of Bryn-Melyn quarry, near Bala, Merionethshire; in fine gritty olive schists above Parklane, 
Shropshire. 
CoNULARIA SUBTILIS (Salter, in Appendix). Pl. 1. L. fig. 24. 
Sp. Ch.—Pyramidal, section rhomboidal (the amount of the angles varying from pressure), each face 
divided by a fine longitudinal median line (or sometimes slightly approaching the inner or outer suture); sides 
of each face meeting at an angle of 12° or 15°; transverse furrows very minute, broad, flattened, much less 
than their thickness apart; separated by very narrow impressed sulci, bent at an angle of about 130°; about 
eight, or near the extremity ten, in the space of one line. 
This species is distinguished from the CO. cancellata of the Silurian rocks, and the much more nearly allied 
Devonian C. tenwistriata, Sandberger (C. Gerolsteinensis, @ Arch. and Vern.), by the smaller angle at which 
the sides meet, or more slender figure, very much finer transverse striation, and these angulated strize being 
very much closer together in proportion to their own width. ‘The striation is scarcely visible to the naked eye 
in most specimens, and it is therefore difficult to see, even with a strong lens, whether they are crossed by a 
longitudinal striation ; a few points, however, seem to be minutely crenulated. 
Position and Locality—Upper Ludlow of Brigsteer, and Benson Knot, Kendal, Westmoreland. 
Explanation of Figures—PI. 1. L, fig. 24, entire specimen, natural size; fig. 24a, portion of surface 
magnified. 
6th Class) GASTEROPODA. 
Nearty all the Gasteropoda enjoy powers of locomotion, and receive their name from the gastric surface 
of the body being flattened into a disk-like foot for creeping; they inhabit salt or fresh water, or the land; they 
are all provided with a distinct head, usually furnished with two tentacles, and perfectly formed eyes; the mouth 
is provided with contractile lips, and two or three horny jaws; frequently the tongue is strap-shaped, and set 
with sharp, hooked points, serving either to rasp sea-weed food for the phytivorous groups, or capable of boring 
holes through shells to reach the food of the carnivorous genera; the mouth opens into a long winding cesopha- 
gus, receiving at the sides the ducts of large salivary glands; this ends in a large oval stomach, from which an 
intestine extends, winding through the great liver and ovary, passing through the branchial cavity, along the base 
of the gills, terminating at the branchial opening, usually on the right side of the head; in some genera the 
stomach is armed with calcareous spines, or as in Bulla with three large grinding plates, concave outwardly. 
The liver is extremely large and lobulated; the ovaries are large granulated masses enveloping the intestine, 
opening into a large oviduct (which is also the uterus of the ovoviviparous species) running parallel to the inner 
edge of the rectum, separated from it by a slender renal duct, and all opening at the same point ; the testis forms 
