VERMETIDAE 143 



heavily beaded, spiral cord. Operculum, corneous, thin, paucispiral, brown 

 and with lamellate growth lines. Moderately common in sand below low- 

 water line. Known for years as A. granulata Lamarck which, however, is a 

 later name. 



Architectonic a krebsi Morch Krebs' Sun-dial 



Plates 4-0; 2iy 



North Carolina to southeast Florida and the West Indies. 



% inch in diameter, similar to A. nobilis, but glossy-smooth on top 

 except for two microscopic spiral threads above the suture, with a smooth 

 rounded base and with its deep umbilicus bordered by 2 beaded spiral rows, 

 the innermost having about 30 bar-like beads (in contrast to 12 in nobilis). 

 Operculum chitinous, brown and multispiral. Uncommon from 16 to 63 

 fathoms. Provisionally placed in this genus. 



Architectonica peracuta Dall Keeled Sun-dial 



Plate 4n; figure 2 2g 



Southeast Florida and the West Indies. 



% inch in diameter, similar to nobilis^ but smaller, with the spire much 

 flatter, whorls almost smooth, periphery very sharp, and without color spots. 

 Rare in 45 to 73 fathoms. 



Family VERMETIDAE 

 Genus Petaloconchus H. C. Lea 1843 



Petaloconchus nigricaits Dall Black Worm-shell 



Plate 2ie 



West Coast of Florida. 



Lives in closely packed colonies of long, worm-like shells about 2 to 4 

 inches in length; each tube is about % inch in diameter. Shells rarely coiled, 

 except at the beginning. Moderately fragile, gray to rusty-brown in color, 

 and weakly sculptured spirally and longitudinally. Colonies of this species 

 frequently form large reefs or banks. 



Petaloconchus irregularis Orbigny Irregular Worm-shell 



Plate 2 id 



South half of Florida and the West Indies. 



Similar to nigricans, but greatly coiled, and with heavier, larger shells 

 which are strongly rugose. Occurs in compact masses attached to rocks and 

 other shells. Color dark brownish. P. erectus Dall is smoother, pure white 

 in color, and with the last part of the tube sticking straight up from the 



