ie SPECIES OF THE SYSTEMA. 
Chttow tuberculatus. 
In this shell, also, the first moiety (“septemvalyi”) of the 
original diagnosis is valueless. Other more valid characters, 
however, are here mentioned,—numerous enough, indeed, for 
clear definition in most genera, yet not so in this especial one, 
which requires an elaborate detail of the peculiarities of sculp- 
ture. As the expression callous tubercles (‘‘ tectum supra tu- 
berculis calloso-elevatis”’) is not more inappropriate than scales 
for the bead-like masses which clothe the connecting ligament 
in the “‘scaly-margined” Chitons of modern terminology, and 
“tectum” is peculiarly significant of their densely packed 
array, the tuberculatus of Linneus was referred to that group 
by some of the earlier writers upon Conchology.* If we un- 
derstand, then, “ corpore tuberculato” in that light, the species, 
as it appears at first in the tenth edition, is manifestly the 
squamosus of Born; for the shell is there defined by a wholly 
harmonising synonymy, which is not opposed to the essentials 
of the diagnosis. ° Petiver’s figure (correctly cited there as 8, 
not 4 as in the twelfth edition) is an excellent representation of 
that shell, and the language of Sloane applies most exactly to 
the same species: the remaining reference (Mus. Ad. Fr.) is 
merely to a name without figure or description appended. The 
additions in the twelfth edition are rather against this alloca- 
tion; for although the “ arcuato-striate ” is very suggestive of 
the peculiarly characteristic arched grooves of its central areas, 
and raised tubercles ( harum 1 et 7 adsperse tuberculis ele- 
vatis”’) are certainly present on its terminal valves, yet the 
special indication of the particular plates which are furnished 
with them insinuates their absence from the rest. It is not 
impossible, indeed, that the raised triangles, being peculiarly 
lable to abrasion, were worn smooth in the typical specimens, 
but this is purely conjectural, and, as our author did not possess 
* Spengler, in his Monograph of this genus (Skrivt. Naturhist. Selskab. 
vol. iv. pt. 1), cites the vignette 16 of the eighth volume of Chemnitz’s 
“Conchylien’ (p, 252, f. A), which represents a seven-valved form of Wood’s 
fasciatus, 
