148 
SILURIAN. 

Case and 
Column of! 
Drawers. 
Reference to McCoy’s 
Synopsis: and Figures of Genera. 

FC 
Gd2 

Gd2 
Gd2 



Names and References; Observations, &c. 
Numbers and Localities. 


Leptena, p. 235. 
a 
OL 
Leptena, p. 23 


Ludlow rocks) and yet preserve their cha- 
racters unimpaired, Leptena Duvalii is 
one of its extreme Dudley forms. It is 
equally common in sandy, muddy and lime- 
stone deposits; but appears to prefer the 
calcareous mud, 
Chonetes, Fischer. All the Productide, to which 
this shell belongs, have spines in some part 
of the surface. Chonetes has them confined 
to the hinge-line of the ventral valve. Car- 
boniferous species are large and finely 
striated. Devonian ones coarsely ribbed, 
often. The Silurian forms are small, and 
often striate roughly or are smooth, some- 
times they are minute shells. 
Chonetes lata, Von Buch sp. (Siluria, 2nd ed. 
pl. 20, fig. 8, C. striatella, Dalm. sp. Davidson, 
Sil. Brach. t. 49, figs. 23—26). Of all the 
common Ludlow shells this is the commonest; 
but it is rarely found in Wenlock limestone, 
and occasionally reaches May Hill sandstone. 
It has coarse strive and spines along the 
hinge, and thus is easily distinguished from 
the species of Leptena proper. 
Chonetes levigata, Sow. (Leptena levigata, 
Sow. Sil. Syst. Siluria, 2nd ed. pl. 20, fig. 15). 
Smooth, with extended ears, and extremely 
common in muddy Wenlock Shales. McCoy 
has occasionally mistaken this for other 
species (Orthis parva for instance). 
Chonetes minima, Sow. (Lepé. minima, Siluria, 
2nd ed. pl. 20, fig. 16). 
Chonetes minima, Sow. var. Grayii, Davidson 
(Sil. Brach. p. 334, t. 49, figs. 15—19), 
Leptena Grayii, Davidson (Bull. Soc. Géol. 
Fr, 2nd ser. Vol. V.). 

749, outside ventral valve; 
a, 750, interior (cast) ditto; 
a. 751, young; Dudley, 
F.C. 
b. 789, Myddleton Park, 
Caermarthen. 
b. 790, Clungunford, Shrop- 
shire; b. 791, near Pool; 
b. 792, Keeper’s Lodge, 
Golden Grove. 
b. 794, W. Shale, Llanfair, 
Welchpool ; b. 795, Bed of 
Dee, Llantysilio. 
b. 788, Dudley, F. C. 
