V( l889 n '] PROCEEDINGS OP THE NATIONAL MUSEUM. 345 



one of these strongly sculptured forms lias all the threads behind the 

 periphery undulated or granulous, forming a variety which may be 

 called G. Goppingerl var. cy ma turn. 



Calliostoma ridensis sp. nov. 



Plate xii. Fig. 5. 



Shell of a waxen color, nearly obscured by clouds, flam mules, and 

 articulations of lighter or deeper flesh color; whorls eight, somewhat flat- 

 tened above, angulated around the base, spirally granulosely threaded; 

 apex pointed; nucleus small, white, dextral ; spiral sculpture of alter- 

 nately larger and smaller threads, of which at the beginning of the last 

 whorl there are six each between the sutures; the paired thread on 

 which the suture runs and the next primary behind it are distinctly 

 wider than the other primaries ; all are set with close rounded granules, 

 which are only moderately prominent; the interspaces are about as 

 wide as the secondary threads; the base has about a dozen rather strong- 

 spirals, with subequal interspaces, but no secondary finer threads; trans- 

 verse sculpture only of lines of growth ; the whorls and base are only 

 slightly convex; aperture subquadrate, the outer lip sharp; pillar stout, 

 short, a little angulated at its anterior point, pearly, and hardly reflected 

 over the imperforate umbilical region. Maximum altitude of shell, 15; 

 maximum diameter of base, IP"" 1 . 



IIab. — Rio Janeiro, on the Encuados Islets, XT. S. Exploring Expedi- 

 tion. Albatross Expedition at Station 27613, off Rio, in 59 fathoms, 

 mud; temp rature 57°; Stations 276f and '2165, off Rio la Plata, in 10 

 to 12 fathoms, sand. 



This species recalls G. jucundum Gould, from New Zealand, and G. 

 euglyptum Adams, from Florida, but is sufficiently distinct from either. 

 It is less elegantly painted than G. jucundum, and the same may be said 

 of its relation to the finer specimens of C. euglyptum, which also has its 

 whorls more rounded and its flammules more regular. 



G. ridensis is very apt to be overgrown with Polyzoa ; few of the speci- 

 mens are free from them. The operculum and soft parts are as usual 



in the group. 



Genus MARGARITA Leach. 



Subgenus TUROICULA Dall. 

 Tureicula Dall, Ball. Mas. Coinp. Zool., ix, p. 42,1881. 



This group is remarkable among Trochidae for its large size and thin 

 shell with delicate green epidermis and reflected peristome like a land 

 shell. The type of the group is small compared with the others now 

 known, but has the characteristic surface sculpture and form, though 

 no perfectly adult and complete specimen has yet come to hand. The 

 voyage of the Albatross has given us two tine species from the Pacific 

 belonging to this group, which are perhaps the finest mollusks collected 

 during the voyage. 



