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SUPPLEMENT TO THE BRITISH 
around Glasgow have I detected perforations ; these are smaller, more numerous, and 
more regular than any perforations I have yet seen on the other species of Productus. 
They are just visible to the eye vi^hen looked at through a good pocket-lens, but are 
better seen under a low power of the microscope. Both specimens are decorticated on 
the outer shell, but little patches of shell that remain show that the perforations did not 
extend to the surface. 
"13. Productus Jimbriatus. — The numerous transverse rows of external tubular spines 
in this species pass through the shell and appear on the inner surface of the valves as 
raised tubercules. Amongst these are to be observed a few irregular and widely set 
perforations, which in this thin-shelled species appear as openings on the surface of the 
shell on some specimens, while they appear to be absent in others, facts possibly due to 
mineralization of the shell-structure. 
" 14. Productus scabricidus. — I had almost come to the conclusion that no perfora- 
tions existed in this species after a close examination of numerous specimens from several 
localities ; but I have since discovered that the inner surface of the dorsal valve of 
specimens from the limestone at Trearne, Beith, Ayrshire, show widely set perforations 
passing outwards, along with a numerous and very minute, but rather faintly marked, 
series of perforations that occur amongst the larger, all over the inner layer of shell. 
This is the same limestone as that from which you have drawn the specimen of Pro(5?. 
scahricidus with the fringe of long tubular spines (Sup., PL XXXV, fig. 3). The 
external tubular spines appear on the inner surface of the dorsal valve as blunt, raised 
tubercules upon the ridges of the shell. The larger perforations, on the other hand, 
exist in the form of neat round pores, varying in distance from one another about 
from Y^th to |^th of an inch or more apart, and always placed in the hollows between 
the ridges. In their wideness apart these perforations resemble those seen in P. Jimbri- 
atus more than any of the other species of Productus. There is one other character in 
Prod, scabriculus which I have observed, and which, I think, has not yet been described. 
On one specimen in my collection I find three broad transverse bands of spines on the 
frontal margin of the ventral valve, not unlike those seen in Prod, punctatus ; and, like 
that species, in each of the bands numerous small, hair-like, tubular spines are arranged 
under the row of larger spines that are placed on the highest line of the band. Higher 
up on the shell these bands disappear, and the valve presents the rough irregular tuber- 
culated appearance so characteristic of P. scabriculus. These bands of larger and smaller 
spines are seen on other examples, but less perfectly preserved than on the specimen 
referred to. 
" 15. Productus undatus. — I have observed no perforations in this species, but if such 
do exist I think they would be much like those of P. cora. 
" 16. Productus pustulosus. — English specimens in the Hunterian Collection, Glasgow, 
show a numerously perforated inner shell-layer, the perforations not reaching the outer 
surface of the valve. 
