372 Reviews—Keeping’s Fossils of Upware. 
describing some species of Chonetes from Mayenne, and could find in 
their shell not a vestige of perforations, I requested my valued 
friend Mr. Young to kindly examine well-preserved specimens of 
Chonetes Laguessiana, De Kon., in order to ascertain whether their 
shell was perforated and in what manner. Mr. Young has also 
examined the shell structure of the three species from Mayenne, 
viz. C. plebeia, C. tenuicostata and C. sarcinulata, and although the 
shell was much altered from mineralization, after having been etched 
with acid, he found perforations, but that they did not reach the outer 
surface, and slanted towards the beaks, as he has described to be the 
case in C. Laguessiana. At my request Mr. Young has likewise 
examined the shell structure of Chonetes armata, from the Devonian 
of Ferques, and found no traces of perforations on the outer surface 
of the valves, but having placed some of them in acid and watched 
them carefully as the etching went on, he found that the perforations 
in each case did not begin to show themselves until he had reached 
close to the inner layer of the valves where they appear in the shell 
structure as a series of little greyish-white tubes, slanting upwards 
towards the beaks of the shell as is seen in Chonetes Laguessiana. 
These punctures can be seen on the interior surface of the valves. 
None of the specimens, however, showed the least trace of that outer 
series of minute perforations so beautifully displayed on the ribs of 
well-preserved examples of C. Laquessiana. 
In pages 295—302 of my Carboniferous Supplement, Mr. J. 
Young gives the results of his minute and lengthened examination 
of the shell structure in the genus Productus, and which satisfied 
him—First, that the perforations are seen only on the inner layers 
of the shell, and that, in no instance, except doubtfully in Prod. 
mesolobus, do they show themselves on the outer surface of the shell. 
Secondly, that the perforations enter from the interior surface of the 
valves and gradually get smaller as they pass outwards through the 
substance of the shell, and are lost before they reach the outer sur- 
face, so that it is only on the interior surface of the ventral and 
dorsal valves that these perforations are seen, or where the outer 
layers of the shell are decorticated or stripped off, as is often the case 
where the specimens have been extracted from hard limestone. 
Thanks to Mr. Young, we now know the true nature of the per- 
forations in the genera composing the family Productide, and he has 
ascertained at the same time that the shells of Streptorhynchus and 
Strophomena, are only perforated in the inner layers of the shell as 
in Productus and Chonetes. 
Tee ES | Vie WV Se 
Uaeoee sys 
Tue Fosstns AND PALmoNTOLOGICAL AFFINITIES OF THE NEOCOMIAN 
Deposits oF Upware AnD Brickuinn. By Waiter KeEeprine, 
M.A., F.G.S. pp. xi. 167. (Cambridge, 1883.) 
Wee work before us is the Sedgwick Prize Essay for the year 
1879, and may be regarded as supplementary to the capital and 
concise Prize Essay for 1873, by Mr. J. J. Harris Teall, entitled 
