GASTEROPODA. PURPURADZ. 141 
with angulated knots; the last whorl tridigitated ; the two left 
fingers short, the right finger long. Height two inches. 
All the digitations are divaricating, and in very fine speci- 
mens are very acute. The respiratory canal is oblique and 
somewhat foliaceous, and being situated a little aside, seems to 
form a fourth digitation, on its right side; the sinus on this 
side is contiguous to the canal in which the respiratory tube or 
rostrum is situated when exserted for respiring. 
This species, which was known to the ancients, is common 
in all the European seas. There are two species beside this, 
which exist in the ocean, and three fossil species. 
Strombus costatus of British authors is the young of this 
species. 
STIRPS V. 
Genus 66. CERITHIUM. 
Cerithium, Lamarck. 
Testa conicé et alté elevata. Sutura tenuis. Apertura pau- 
lum volutata et reflexa. Peritrema tenué perfectum. Ani- 
mal incognitum. } 
Shell conically and highly elevated, its suture slender, its 
aperture at the left voluted and reflexed; its peritreme thin 
but perfect. 
Synopsis Specierum. 
* Testa costis tuberculatis. 
1 retcculatum. Test& rufo-brunned; anfractibus duodecim, 
transversim costatis ; costis tuberculatis ; tuberculis zequali- 
bus in serie quadrupla dispositis, interstitiis reticulatis. 
2. tuberculare. Testa castanea ; anfractibus decem transvyersim 
costatis ; costis tuberculatis ; tuberculis eequalibus in serie 
triplici dispositis ; interstitiis reticulatis. 
3. subulatum. Testa albida; anfractibus quindecim, transver- 
