332 MONOGRAPH OF THE GENUS ARGONAUT A, 



numerous ribs, and particularly by the absence of a sinus and its rib-like or thickened 

 margin. 



5. A. GONDOLA, Dillwyn. Gat. i. p. 335. 



A. navicula ? Soland. Humph. Cat., p. 6. 



A. Crancliii? Leach. Philos. Trans., 1817, p. 296, pi. xii. fig. 1—6. 



A. Haustrum? Dillwyn. 1817, i. p. 335. 



A. raricosta, Blain. Diet, des Sci. Nat., Ixiii. p. 218. 



Inhabits the South Atlantic. Cabinet of the Academy. 



6. A. HiANS, Soland. Dillwyn. Cat. i. p. 334. 



A. niiida, Lam. (ed. of Desh.) An. sans Vert., xi. p. 357. 



Inhabits the tropical and South Atlantic. Cabinet of the Academy. 

 This species, according to D'Orbigny, is found in the Tertiary Subapennine de- 

 posits of Piedmont. 



7. A. OwENi, Adams. Zool. Voy. Samarang. Moll., p. 4, pi. 3, fig. 1. 

 Inhabits the South Atlantic Ocean. Cabinet of the Academy. 



8. A NODOSA, Solander. Humphrey's Cat. p. 6. 

 A. tuherculata, Shaw. Nat. Misc. xxiii. t. 995. 



A. tuberculosa, Lam. An. sans Vert. (ed. of Desh.) xi. p. 357. 



Inhabits the Indian Ocean. 



9. A. CORNUTA. PI. 34, fig. 2. — Form nearly similar to that of A. gondola, but the ribs on the umbo are 



much more numerous and closely arranged, and the ribs and tubercles of the other portions of the shell 

 are more numerous ; back with interrupted undulations and distant unequal tubercles ; whole surface 

 except the umbo minutely papillose. Angle of the lip with a spine nearly at right angles with the 

 length of the shell ; surface white and destitute of polish; submargin of sinus and the spine dark purple. 



Inhabits . Cabinets of the Academy and John S. Phillips. 



This is a beautiful shell of which I have seen two specimens. It is easily dis- 

 tinguished from A. gondola, by its spines being nearly at right angles with the shell's 

 length, by its want of polish and more numerous and smaller tubercles, which are 

 much narrower than in the gondola, and by its color. It has about 45 ribs, while the 

 ffondola has 39. 



o 



10. A. DISPAR. PI. 34, fig. 3. — Ovate-oblong, nearly destitute of polish, white under the epidermis ; surface 

 minutely papillose, smooth on the umbo ; ribs entire, suddenly becoming larger anteriorly where they 

 terminate at the carina in large distant tubercles, about 5 in number on each side ; the remainder of the 

 tubercles very small and closely arranged ; back slightly concave and entire between the series of large 

 tubercles, the rest of the back slightly convex or flattened and tuberculated, except toward the summit 

 where it is entire ; sides flattened or slightly convex; aperture oblong-oval, the lips parallel and straight 

 in th€ middle. 



Inhabits . Cabinet of the Academy. 



