FAMILY ARCADA — NUCULA. 179 
NucuLa RADIATA. 
PLATE XI. FIG. 216. 
Description. Shell rather solid, very oblique, triangular. Surface polished, with minute 
concentric lines, and occasional larger ones ; these concentric lines are rendered waving by a 
furrow running from the beak to the base, parallel to and at a short distance from the anterior 
side. Beaks anterior, large and eroded. ‘Teeth minute, the two series forming almost a right 
angle with each other: four to five in one series, and from nine to ten in the other; the inner 
is deeply crenulated on the margin by numerous strie radiating from the cavity of the beaks, 
but not impressed externally. 
Color. Epidermis thin, ferruginous ; beneath whitish pellucid ; within bluish iridescent. 
Length, 0°18. 
Under this name, I venture to indicate a shell which was obtained by Dr. C. H. Stillman, 
by dredging in the East river opposite Williamsburgh : some thirty or forty other specimens 
were procured at the same time. In the number of its teeth, and the strongly impressed 
radiating strie, it is very distinct from its otherwise strongly allied species N. proxima. 
NucuLa PROXIMA. 
PLATE XII. FIG. 215. 
Nucula proxima, Say, Jour. Acad. Nat. Sciences, Vol. 2, p. 270. 
N. id. Conran, American Mar. Conchology, pl. 6. fig. 2. 
N. id. GouLp, Invertebrata of Mass. p. 103, fig. 63, 
Description. Shell small, solid, subglobose, trigonal, oblique, polished, concentrically 
wrinkled with numerous hardly perceptible striez : beaks somewhat elevated and inclined for- 
wards ; pit of the cartilage very small. Teeth very robust for the size of the shell, long, 
acute, recurved and equidistant ; twelve in number before, and about twenty behind the 
beaks. Margin very minutely crenulated ; the crene extending some distance from the mar- 
gin, but not forming radiated striz as in the preceding. 
Color. Epidermis light olive and very thin ; within pearly white. 
Legth, 0:45. Transverse diameter, 0:35. 
This species, although not yet detected on our coast, will undoubtedly be found, as it 
ranges from Massachusetts bay along the southern coast. It is closely allied to, but as we 
think very distinct from, the preceding. 
23” 
