90 



expanded at maturity into a lobe ; in one of the three only recent species 

 known, A. occidentalis, from the northern shores of Western America, the 

 lobe is simple, in the remaining two A. pes-Pelicani, and pes-Carbonis of 

 the Mediterranean, it is digitated, the shell being of a corresponding- 

 structure. 



Species. 



1. occidentalis, Beck. 2. pes-Carbonis, Broiuj. 3. pes-Pelicani(ii!0.^.)Lam. 



Genus 4. ROSTELLARIA, Lamarck. 



Animal ; elongated, disc divided into two parts, the posterior 

 cylindrical, obliquely truncated, and carrying a horny unguiform 

 operculum upon the truncature, the anterior flattened and 

 rounded, serving the animal to attach itself to solid bodies ; 

 head large and thick, prolonged into a proboscis-shaped muzzle, 

 slit in front ; tentacles diverging, cylindrical, two forked, the 

 inner branch being slim and pointed, the outer truncated at the 

 summit, with the eye situated upon the truncature. 



Shell ; fusiform, prolonged at the base into a canal which is some- 

 times very long and slender ; whorls slightly convex, sometimes 

 furnished here and there with a varix ; lip toothed, or digitated. 



It appears from Ehrenberg's characters of the animal above noticed, that 

 the Rostellarice whose graceful fusiform shells are so much admired by the 

 collector, and are the pride of his cabinet, have a much closer affinity with 

 the Pterocerce and Strombi, than with the Aporrliaides which have been 

 hitherto associated with them, or the Fusi, to winch they were approximated 

 by Eerussac and De Blainville. The disc presents the same peculiar modi- 

 fication of structure as in Pterocera and S trombus; divided into two parts, 

 the animal is said to acquire motion by executing a succession of leaps, 

 instead of the ordinary mode of progressing by dilatation and contraction. 



The Rostellarice may be easily recognized by the elegant fusiform growth 

 of the shell, with its peculiarly dentated, or finely digitated lip ; they are 

 very limited in species, and are principally from China and the Moluccas. 



Species. 



1. curta. Sow. 3. fissa, Desk. 5. Powisii, Petit. 



2. curvirostrum, Lam. 4. fusus (Stromb.), Linn. 



