MOLL ITSC A OF PORTO RICO. 
387 
Drillia albinodata Reeve. 
Pleurotoma albinodala Reeve, Conch. Icon., J, pi. xxxvm, fig. 352, 1846. 
Shell solid, with about ten whorls; suture impressed but not deep, with a slight revolving ridge 
below it, followed by a wide, shallow groove; below this is a somewhat raised nodulous shoulder, the 
nodules are extended toward the base as faint ribs. Below the shoulder there are three or four feeble 
revolving ridges which are swollen into nodules where they cross the longitudinal ribs. Besides this 
the whole surface of the shell is sculptured with exceedingly fine, revolving threads. Varix heavy; 
aperture short; sinus deep, rounded, nearly closed in front, and above it the upper edge of the last 
whorl is raised on the penultimate whorl. On the shoulder there is a white band, and there are two 
white bands on the base of the shell; the rest of it is a dark brown. 
Length of specimen from Porto Rico, 12; diameter, 5 mm. 
One shell, Plava de Ponce reef. 
Drillia albocincta C. B. Adams. 
Pleurotoma albocincta C. B. Adams, Proc. Bost. Soc. Nat. Hist, ii, p. 3, 1845; Tryon, Man., vr, p. 196, pi. xiv, fig. 6 (as Drillia 
zebra Lam.), 1884. 
Shell small, solid, with about eight whorls, with a low shoulder bearing on it a series of tubercles 
which are sometimes elliptical, and at others form two nearly perfect series. Under the suture there is 
a low, slightly tuberculous ridge, and between this and the shoulder a wide, shallow groove. Below 
the shoulder there are several revolving nodulous threads; aperture short, truncate below. The gen- 
eral surface is covered with very fine, revolving threads and is dark brown; the nodules are white. 
Length, 10; diameter, 4.5 mm. 
Arroyo; Puerto Real; Mayaguez Harbor, Porto Rico. 
The two foregoing species belong to a group of closely related and variable forms. Tryon throws 
a number of them into the synonymy of Drillia zebra Lamarck, and it is possible that both the above 
may be merely forms of that species. 
Drillia solida 0. B. Adams. 
Pleurotoma solida C. B. Adams, Contr. to Conch., p. Gl, 1850. 
Drillia fuscescens Tryon (in part), Man., vi, p. 193, pi. xiv, fig. 98, 1881. 
Shell with eight or nine whorls, with rather strong, oblique, slightly flexuous ribs, which end at 
the shoulder; above the shoulder is a wide, concave furrow, and between the furrow and the suture 
is a sharp ridge. Between the ribs are revolving threads which are stronger on the base; aperture 
short, narrowed below. Color dark brown, the spaces between the ribs on the shoulder lighter. 
Length, 10; diameter, 4 mm. 
Island of Vieques, one shell, slightly broken. 
Drillia thea Dali. 
Drillia thea Dali, Proc. U. S. Nat. Mus., vi, p. 328, pi. x, fig. 5, 1883. 
Shell with eight whorls, the first one and a half smooth, the others with delicate growth lines, 
and having about seven or eight strong, slightly curved ribs; these ribs are nearly continuous from 
the apical whorls to the base of the shell, being only slightly cut by the narrow suture, and becoming 
a little fainter at the faintly impressed fasciole; varix distinct, canal somewhat drawn out. Color 
generally that of wet tea leaves. 
Length, 15; diameter, 4.5 mm. 
Aguadilla; Mayaguez, Porto Rico; one dead and broken shell from each locality. 
? Drillia aepynota Dali. 
Drillia xpynota Dali, Blake Report, II, p. 96, pi. xxxvi, fig. 10, 1889. 
Two young, badly worn shells were obtained in Mayaguez, Porto Rico, which may be this. 
Drillia lissotropis Dali. 
Pleurotoma ( Mangilia ) lissotropis Dali, Bull. Mus. Comp. Zool., ix, p.68,1881. 
Drillia lissotropis Dali, Blake Report, ii, p. 91, pi. xi, figs. 3, 4, 1889. 
Shell small, with about eight whorls which are slightly convex, and having ten to twelve nearly 
straight, strong, longitudinal ribs; spaces between the ribs either smooth or delicately spirally striate; 
