306 
SUPPLEMENT TO THE BRITISH 
very near the surface, almost without any " bare" or soil on the top of it, has been decom- 
posed to a very great extent by the passage of rain-water charged with carbonic 
acid. Not only is the top portion of the limestone decayed, Tsut the water taking 
advantage of the "cracks" and "breaks," has decomposed it from the top to bottom, 
sometimes into spaces a foot or more wide. There not having been enough of water to 
carry away the undecomposed siliceous and aluminous matter, the rotted limestone 
occurs in the cavities as a rusty powder. The remains of sponge spicules, Producti, 
corals, fish, teeth, &c., are found in it in great abundance. 
35. Productus humerosus, Sow. Dav., Carb. Mon,, PL XXXVI, figs. 1, 2 (internal 
cast) =z Shell (P. sub-loevis), p. 177 ; PI. XXXI, figs. 
1,3; PI. XXXII, fig. 1 ; PI. LI, figs. 1, 2, p. 234 ; 
and Sup., PI. XXXVI, fig. 2. 
Productus humerosus, Sow. Min. Conch., f5g. 322, January, 1822 (internal cast 
only). 
— sUB-L.CTis, lie Koninc/e. Anim. foss. du Terr. Carb. de Belgique, pi. x, 
fig. 1 (shell), 1843. 
Up to the month of April, 1870, Productus humerosus and Prod, suh-lcevis were 
considered two distinct species, and I was consequently much surprised when, on the 7th 
of April, I received from Mr. James Eccles the following communication : — " Some weeks 
ago I obtained some specimens of Productus from the Mountain Limestone near Caldon 
Low, in Staffordshire, which, from their external character, I unhesitatingly referred to 
Productus sub-lavis. One of the specimens was broken, and exhibited the cast of the 
large conical depressions in the shell in the direction of the beak, characteristic of Prod, 
humerosus (Sup., PI. XXXVI, fig. 2). I have since intentionally broken other specimens in 
which the same character is observed. As the determination of Productus humerosus 
has been made from internal casts alone, and as I am under the impression that the internal 
structure of P. sub-lcBvis is unknown, it has occurred to me that the two species are 
identical." 
Mr. Eccles having sent me his specimens for inspection, both myself and Professor 
de Koninck, to whom I subsequently showed them, are in a position to confirm this 
discovery. As the name humerosus is the oldest, according to the laws of priority, it will 
have to be preserved for the species, and that of sub-lcevis put among its synonyms. I 
have nothing further to add to the description I have given of this very remarkable species, 
but I append a figure I have made from one of Mr. Eccles's specimens. 
