264 ARGONAUTA. 



3. tuberculosa (f. 3), Lamk. — Testa convexa, rotunda ; rugis 

 in tuberculis divisis ; carina lata, tuberculis magnis subdistantibus; 

 apertura lata, auriculis productis, lateribus convexis. Obs. Much 

 more convex and rounded, with the radiating ribs broken up into 

 small tubercles. 



4. gondola (f. 4), Dillwyn. — Testa semiorbicularis, valde 

 convexa, pallide fusca; rugis validis, distantibus, alternatim bre- 

 vioribus ; carina latissima, distanter tuberculata ; apertura late 

 hiante, auriculis exterius productis. Obs. This is the widest shell 

 of the genus, the aperture widely gaping, and the keel very 

 broad, and the auricles produced and twisted outwardly. 



5. hians (f. 5, 6), Dillwyn. — Testa convexa, subelongata, 

 fulva ; rugis leviter elevatis, alternatim brevioribus ; carina lata 

 obtuse et distanter tuberculata ; apertura lata, lateribus convexis, 

 auriculis rotundatis minime productis. Obs. As compared with 

 the preceding, the ribs are not so pronounced, the tubercles not 

 so large and more obtuse, the mouth is narrower, and the 

 auricles not produced nor twisted outwards in this species. 



6. Oweni (f. 7, 8), Ad. and Reeve. — Testa semiorbicularis, 

 subcompressa, fulva ; rugis validis, alternatim brevioribus ; ca- 

 rina lata, valide tuberculata ; apertura oblonga, prope spiram an- 

 gustata, lateribus compressis, auriculis vix productis. Obs. The 

 ribs are more distinctly pronounced, and the sides of the shell, 

 particularly near the axis, much more compressed than in A. hians. 



