LINGULID. 47 
and occurs very often together with spines of Onchus and other Fish-remains. It is a 
much larger and more oblong and rectangularly shaped shell than the one met with in such 
profusion in the “ Downton sandstone,” underlying the “ Passage-beds” above mentioned ; 
and it has been a question with Mr. Lightbody whether the “ Downton sandstone” shell 
should be considered specifically the same as Z. cornea proper, since it appears to differ 
from it in shape, size, and locality. 
Now, it is probable that Sowerby was himself impressed with the same uncertainty ; 
and it was to the small elongated form from the “ Upper Ludlow rock” or ‘“ Downton 
sandstone” that he originally applied the designation of Z. minima ; for under “ Upper 
Ludlow rock” he makes no reference to Z. cornea; and the dimensions given to L. 
minima coincide exactly with the average proportions of the specimens of Lingula which 
occur in the “ Downton sandstone.” ‘Ihe “ ‘Tin Mill beds,” assigned by Sir Roderick to 
his typical LZ. cornea, are identical with the Passage-beds ; and are higher up in the scale 
than the ‘Downton sandstone” where ZL. minima is located. 'The narrow form, or the 
one last named (states Mr. Lightbody) does not seem to appear till we get to the 
«'Trochus-bed,” a sandy bed forming the base of the “ Downton sandstone,” and, near 
Ludlow, lying about a yard above the Bone-bed, and containing a new Modiolopsis, 
Platyschisma (Trochus) helicites (though the last-named shell is also found in the mud- 
stone intercalated with the Bone-bed), and a vast abundance of Beyrichia Kledeni. 
Thanks to Mr. R. Slimon, I have likewise been able to examine a number of Lingule 
termed Z. cornea by Sir R. Murchison and Mr. Salter in their paper on the ‘‘ Uppermost 
Silurian Rocks near Lesmahago, in Scotland” (‘ Quarterly Journal Geol. Soc.,’ 1856). 
These Lingulz, as in the “ Downton sandstone,” partake of the same character, but are 
smaller and more elongated than the typical Z. cornea from the Passage-beds above. I 
would, therefore, (notwithstanding the statement made by Prof. M‘Coy at p. 251 of his 
‘British Pal. Fossils,’ namely, that Zingula minima does not show the slightest differ- 
ence from Z. cornea that he can perceive,) feel disposed to retain the term cornea for the 
form first described in the ‘ Silurian System,’ and that of mzazma for the smaller and more 
elongated shell found in the “Downton sandstone” and Trochus-bed at Ludlow and 
Lesmahago. 
Position and Locality. L. cornea occurs, therefore, in the “ Passage-beds,”’ which 
Sir Roderick Murchison considers to belong to the uppermost portion of his Silurian 
system (see ‘ Siluria,’ chap. vii, p. 154, 1859). The typical form is abundant at Tin Mill, 
Downton ; in the railway-cutting at the north end of Ludlow ; at Brockhill and Steventon 
turnpike, near Ludlow.’ [At p. 24 of his ‘Synopsis Silurian Fossils, Ireland, Prof. 
‘1 Mr. Lightbody, who has devoted much care to the study of the Ludlow locality, seems disposed to 
concur with Mr. Salter in considering these ‘‘ Passage-beds”’ as part of the Lower Old Red Sandstone, 
because, according to the Rev. W. S. Symonds’ section at Ledbury (‘Quart. Journ. Geol. Soc.,’ vol. xvii, p. 155), 
where the beds are continuous, they are 300 feet above the top of the ‘‘ Downton sandstone.” Though at 
Ludlow the junctions are all obscured, yet there is no doubt of these beds being above the horizon of the 
