PYRAMIDELLIDZ. 411 
The Chem. fenestrata is very distinct, as is the elegant 
C. scalaris, which latter we have frequently, during the last 
thirty years, taken at Exmouth, varying in the number of 
ribs, but never in a living state. Since then, both have been 
taken alive, and, in the examinations, we have ascertained 
that the Chem. rufescens of the ‘ British Mollusca’ is only a 
variety of the “ scalaris.” We have shown, in the descriptions 
of Chem. interstincta and C. indistincta, thei specific points, 
and that the Chem. clathrata is scarcely a variety of the 
latter. 
The elegant C. decussata, the “arenaria” of Montagu, 
abounds at the same place in the coralline zone, and with 
the well-known C. Scille and C. acicula require no remark, as 
they are undisputed species. 
The C. affinis of authors, we believe, is a variety of the 
C. acicula, a very variable species in respect of the tumidity 
of the volutions and depth of the divisional lines, as well as of 
the texture of the shell. The C. clavula is very distinct, and 
everything relating to former impressions is fully explamed 
under that title. We think the Aclis nitidissima of authors 
will, when the animal is observed, prove a Chemnitzia; the 
Aclis unica, formerly conjectured by me to be a Chemnitzia, 
has this year (1854) been discovered, and is described as Rissoa 
unica, m the elongated section of that genus. 
The beautiful Chemnitzia Gulsone is our own discovery 
more than thirty years ago. I have not a character to add or 
omit from my original description in the Annals of Natural 
History, except that after the phrase of the specific character, 
“peripheria integra,” interdum interrupta may be added, as 
my specimens differ. The apex is subreflexed—indeed every 
character denotes the Chemnitzian animal; there is not a 
single point of the Rissoa in it. 
The Chem. formosa is a slender Chem. rufa. 
The beautiful, but common, Chem. elegantissima is the 
staple commodity amongst the shells at Exmouth, where all 
its varieties occur, but never alive—probably because they 
inhabit the rocky portion of the lamimarian zone, far beyond 
the lowest tides, where the dredge cannot work; they must 
