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ART. XXXII. — Monograph of the Genus Argonauta, Linne, with descriptions of five 



new species. 



By T. A. Conrad. 



ARGONAUTA, Lin. 



1. A. ARGO, Lin. 1758, Syst. Nat. x. p. 708. 

 Lam. An. sans Vert. (ed. of Desh.) xi. p. 355. 

 Blainville. Diet, des Sci. Nat. xliii. p. 212. 

 Poll. Test. Sicil. iii. t. xl. fig. 1. 



Inhabits the Mediterranean. Cabinet of the Academy. 



Blainville regards the Mediterranean shell, usually confounded with the" Indian 

 species, as the type of Argonauta argo, Lin. The two have certainly a^marked dif- 

 ference in character, and Linne refers to Lister's t. 554, which is the Atlantic''and 

 Mediterranean shell, described by Lister as " non auritus." The lip varies in form, 

 sometimes rounded and sometimes angular, but I^have not seen a specimen with[^a spine 

 or horn which is always present in the allied species [compressa). 



2. A. COMPRESSA, Blain. Diet, des Sci. Nat., xliii. p. 212. 

 Gualt. t. 11, fig. A. 



Inhabits the Indian Ocean. Cabinet of the Academy. 



This species is easily distinguished from the preceding by its larger and fewer ribs, 

 but particularly by the regularly rounded sinus with a thick rib-like margin ending 

 above in a short spine. It grows to a large size, a specimen in the Academy measuring 

 8 J inches in length. The young shell has the thick lip margin at the sinus, and the 

 spine, and is strikingly dissimilar to the young of the Mediterranean shell generally 

 confounded with A. argo of India. 



Neither this species nor the Argo appear to inhabit the North Atlantic, otherwise 

 they would probably be met with in company with A. Mans, in the vicinity of the 

 Canaries, and like that species sometimes cast ashore ; but it would seem that a vast 

 space of ocean separates the Argo and compressa. The South Atlantic shell of the ■ 

 American coast differs in somerespects from A. argo, and is probably a distinct species. 



4. A. PAPYRIA. PI. 34, fig. 1. — Much compressed, extremely thin, ribs very numerous, lip without a spine 

 at the angle which is rounded ; sinus of the lip closed by u calcareous glo.ssy deposit, with ac acute and 

 concave margin. 



Inhabits . Cabinet of the Academy. 



Differs from either of the preceding species by its more compressed form, more 



