ARGONAUTA. 137 



Shell with distant ribs, laterally compressed tubercles on the 

 carina ; surface smooth, polished. 



Pliocene of Piedmont (not living in Mediterranean Sea) ; 



So. Atlantic Ocean ; China. 



I figure the typical A. hians (fig. 101), from Adams and Reeve, 

 Voyage Samarang, and the eared form (A. gondola, Dillw., figs. 

 100, 102), with its animal. 



A. OWENII, Adams and Reeve. PL 46, figs. 103-105; pi. 47, 



figs. 106, 107. 



The ribs are somewhat closer and the tubercles on the carimv 

 are sharper and not laterally compressed as in A. hians; the sur- 

 face is shagreened. 



S. Atlantic Ocean. 



A. cornuta, Conrad (figs. 104, 105), is an eared form of the 

 same species. A. dispar, Conrad (106. 107), d liters only in the 

 unusual development of some of the lateral carinal tubercles, 

 and in a portion of the back being tuberculate neither of them 

 specific characters. 



A. CONRADI, Parkinson. 



Ribs rather distant, not furcate, long and short alternately, 

 portion of the back studded with small tubercles ; tubercles on 

 anterior and posterior thirds of carina 1 small, nearly obsolete; 

 on the middle third of each carinae, seven very large tubercles, 

 broad at the base, laterally compressed. Aperture angled, 

 spineless. Surface shagreened. 



This species has never been figured ; it is not apparently very 

 distinct from A. Owenii, and perhaps, by its laterally com- 

 pressed tubercles, may unite that species with A. hians. 



New Nantucket, Pacific Ocean. 



A. KOCHIANA, Dunker. PI. 47, figs. 108-110. 



Differs from A. hians in the ribs being closer and less prom- 

 inent ; from A. Owenii in the tubercles on the carina' being but 

 little prominent and finally becoming obsolete, and in the surface 

 of the shell being polished. Probably all these forms should be 

 referred to A. hians. 



Chinese Sea. 

 18 



