Dr. Thomas Davidson—Note on Chonetes, ete. ovl 
the beak slant inwards at the greatest angle, the inward con- 
vergence of the tubes decreasing on either side towards the outer 
edge of the shell. When the tubes, however, reached the car- 
dinal edge of the shell, and were prolonged outwards in the form 
of spines, instead of continuing to converge towards the beak, they 
became suddenly bent in the opposite direction, so that they after- 
wards diverged from the beak in a slanting manner. 
Chonetes Laguessiana, de Kon., is the only abundant Scottish 
Carboniferous species, that is of sufficient size, and thickness of 
shell, to allow of my examination, by means of etching with acid, 
of both its outer and inner surface. I find, however, evidence in 
other of our smaller Chonetes, of similar tubular openings on the 
outer surface, and raised tubercules on the inner surface of the shells, 
that agree with those seen in C. Laguessiana, and I have no doubt 
but that the whole genus was characterized by similar perforations, 
but modified in their arrangement in the several species. 
In bringing this note to a close I have only to remark that the 
points of interest noted in my investigation of the shell structure of 
C. Laguessiana are four: these are, Ist, the occurrence on the ribs of 
both valves of a series of wide-set tubular openings or bases of spines, 
that do not pass inwards through the thickness of the shell; 2nd, a 
row of very minute close-set pores that are placed along the central 
line of each rib, but which descend only a very short distance into 
the shell substance, and then disappear; 38rd, a series of wide-set 
perforations, not visible at the surface, but which start near the 
middle layer of the shell, and are continued in single rows between 
each rib in an upward slanting direction through the shell, and appear 
upon the inner surface of the valves as numerous raised tubercules ; 
4th, a row of tubular spines in the cardinal edge of the ventral 
valve that open with round orifices on the inner surface of the shell, 
the tubes at first converging towards the beak, but on arriving at 
the outer edge being prolonged as spines and bending suddenly in 
the opposite direction. So many points of structure as are here noted 
cannot, I think, fail to make this species of Chonetes always an 
interesting object of investigation to the Conchologist. It wouid 
also be interesting to learn if similar structures and arrangement of 
the cardinal spines existed in other large and well-preserved species 
of the genus. 
VI.—Notr on CzHoneres LAGUESSIANA. 
By Tuomas Davinson, LL.D., F.R.S., F.G.S., ete. 
T page 37 of his chapter ‘‘ On the Minute Structure of the Shells 
of the Brachiopoda,” and forming part of my work “ On British 
Fossil Brachiopoda,” Dr. Carpenter says :— “‘ Chonetes.— Of this 
genus, also, I have examined two species, armata and lata, both of 
which are perforated,”—but Dr. Carpenter does not explain in what 
way they are perforated, viz. whether these perforations pass through 
the entire thickness of the valve, or are restricted to a small portion 
of its thickness as in Productus. 
Mr. D. Oehlert, of Laval, having recently written me that he was 
