ACADEMY OF SCIENCES. 303 



This lovely species has no relations with A. syharitica, Dall, and rosacea, 

 Cpr., except those of color. The two latter are much smaller and the rose 

 color is much lighter and ditferently disposed. Its nearest allies are some 

 varieties of A. paliua, in none of which have I observed any approach 

 to the color of this species, and which have a different nucleus, and the 

 sculpture in slender rounded riblets instead of sharp threads. The shell 

 of patina is also in general much more solid and thick. The animal 

 partakes of the rosy hue of the shell except the margin of the mantle 

 which is furnislied with brown dots. It belongs to the subgenus Colli- 

 sella. It is worthy of note that when there is a brown marking on the 

 exterior, in the region of the submarginal internal mottled band, the latter is 

 interrupted by a white space corresponding in size and width to the external 

 marking. In spite of the very great variations in the species of this genus, I 

 feel sufficiently confident in regard to the distinctness of this form to describe it 

 as a well marked species, excelled in beauty by none. 



Argonauta expanfa, Dall, n. s. 



Shell of moderate size, of nearly two involute whorls. Aperture widely ex- 

 panded near the spire, rather narrow in front. Carinaj rather blunt, furnished 

 with about thirty alternate projections, those behind the posterior edge of the 

 aperture above and below, being tipped with very dark brown. The promi- 

 nence of the projections decreases in the middle of the back, and they become 

 larger and more prominent toward the anterior edge of the aperture. The pro- 

 minence of the lateral radiating folds varies in like manner. Of these about 

 twenty-three start from the axis of the shell, which is drawn out behind the 

 lateral expansions of the aperture and supports them. There are about twenty- 

 six intercalary folds. The spire behind the posterior edge of the aperture is 

 more or less tinged with brown, and there is a livid brownish purple coloration 

 on the lateral extensions of the axis and that part of the shell adjacent to them. 

 The interior of the shell is smoothly polished, the exterior, especially on the 

 protuberances of the carinte.is covered with a multitude of exceedingly minute 

 rough pustules, which give a very rough, harsh feel to the shell, and under a 

 lens appear hemispherical. Laying the shell upon its aperture, with the apex 

 posterior, we have the following measurements. Total length 3.25 in. Width 

 of dorsal area posteriorly 0-32 in., do. anteriorly O'T. Height of shell 20 inches. 

 Total extension of axis from end to end. 4 inches. Total length of aperture 

 2-25 inches, length from the anterior edge of the spire to the anterior edge of 

 the aperture Id inches. 



Habitat, in the Gulf of California. 



This pretty and peculiar argonaut possesses an assemblage of characters not 

 common to any described species, th(jugh there are several which have a some- 

 what similar lateral extension of the axis. The dry ova still adhere to the 

 inner side of the spire, and the shell is evidently fresh. I have seen one other 

 specimen smaller than the one described, and collected at the same time. The 

 only other species known from the same locality, {A. Pacijica, Dall,) is much 

 compressed, has not the lateral extensions and has a different sculpture, beside 

 growing much larger. Colls. Stearns, Dall, Fisher and Harlbrd^. 



