ARGONAUTA. 137 



Shell with distant ribs, laterally compressed tul)ereles on the 

 carina ; surface smooth, polished. 



Pliocene of Piedmont (not living in Mediterranean Sea) ; 



80. Atlantic Ocean; China. 



I figure the typical A. Mans (fig. 101), from Adams and Keeve, 

 yo3'age Samarang, and the eared form {A. gondola^ Dillw., figs. 

 100, 102), with its animal. 



A. OwENii, Adams and Reeve. PL 4r., figs. 103-105; pi. 4T, 

 figs. lOG, 10". 

 The ribs are somewhat closer and the tubercles on the carinae 

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

 face is shagreened. 



S. Atlantic Ocean. 



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

 same species. A. clispar^ Conrad (10(i, 107), differs only in tlie 

 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 carinje small, nearly obsolete ; 

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

 broad at the base, laterally comjiressed. Aperture angled, 

 spineless. Surface shagreened. 



This species has never been figured ; it is not ai^parently very 

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

 pressed tubercles, may unite that species with A. Jiia)h-<. 



New Nantucket, Pacific Ocean. 



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



Differs from A. Mans in the ril)s being closer and less i)rom- 

 inent ; from A. Owenii in the tubercles on the carinte lieing Ijut 

 little prominent and finally becoming obsolete, and in the surface 

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

 referred to A. Mans. 



Chinese Sea. 

 18 



