176 CONCHOLOGY. 



carinated, sub-involuted longitudinally in the same plane ; 

 aperture very large, entire, symmetrical, square in front, 

 slightly modified by the turn of the summit, and provided on 

 each side with an earlike appendage, with thick and smooth 

 edges ; lips sharp. 



Argonauta argo. Argonauta tuberculosa. 



A. nitida. 



A. argo. The Portuguese man-of-war. PI. 35, fig. 1. 



Characterized above ; shell whitish, fragile, keel rather 

 narrow, with sharp-pointed tuberculations ; sides striated 

 transversely, wrinkled longitudinally. 



A. tuberculosa. The tuberculated Argonaut. PI. 35, 

 fig. 2. 



Species more convex at the sides, with nodulous eleva- 

 tions ; keel broader, points more obtuse, 



2. Carinaria. The glassy Nautilus. Three species. 



In form and texture greatly resembling the Argonauta, but 

 distinguished by only having one keel on the whole length 

 of the back. 



Shell symmetrical, carinated or not, very thin, slightly 

 compressed, without spire, but with the summit slightly re- 

 curved posteriorly ; aperture oval and very entire. 



Carinaria vitrea. Carinaria fragiUs. 



C. cymbium. 



C. vitrea. The glassy Carinaria, 



Species very rare and beautiful, thin, papyraceous, very 

 fragile and semitransparent ; a serrated keel rises up its 

 front, and the sides are decorated with ribs parallel to the 

 base, 



C.fragilis. The fragile Carinaria. 



Species smaller, very thin, striated longitudinally, diver- 

 ging from the summit to the margin ; no keel, 



C. cymbium. The minute Carinaria. 



Species not larger than a grain of sand. 



