164 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
most distinct in the right valve; pallial sinus very wide and deep; ligament 
external, prominent. (Tryon. S. S. Conch.) 
Type. Tellina virgata Linn. 
Distribution. In all seas, especially the Indian Ocean; most abun¬ 
dant and highly colored in the tropics. 
Tellina idae Dali, 1891. 
Plate 14, fig. 4. 
Proc. U. S. N. M. f 14, pi. 133; pi. 6, fig. 3. 
Shell ovate-triangular, moderately elongate, white, compressed; exte¬ 
rior of the right valve slightly flatter, and with more prominent sculpture 
than the left valve; beaks small, pointed, prominent, laterally compressed, 
adjacent to each other; anterior part of the shell slightly longer than the 
part posterior to the beaks, evenly and regularly oval, the dorsal and 
basal curves almost identical; posterior dorsal slope steeper, rectilinear, 
obliquely truncate at its termination, the basal curve (behind the perpen¬ 
dicular from the beaks) similar to its anterior part as far as the flexure, 
which is narrow but well marked, its basal end moderately incurved; 
behind it rises to a strong ridge the end of which forms a rostral projec¬ 
tion, behind which, in the right valve, is a deeply impressed line a little in 
advance of the posterior dorsal margin, which is strongly compressed; 
on the left valve there are two lines with a narrow impressed area between 
them, above which the dorsal margin is swollen; in front of the beaks is a 
narrow, acute, deeply excavated, short lunule; behind the beaks is a large, 
narrow, still more excavated escutcheon, most of which is excavated from 
the left valve, which falls short of the right valve a little; the ligament is 
sunken in and about half as long as the escutcheon; it is quite invisible 
on a lateral view of the shell; the left valve is regularly, sharply, closely, 
concentrically grooved, and both are obsoletely, finely, radiately striate; 
the margin between the impressed area of the left valve and the escutcheon 
is more finely grooved than the rest and has a (somewhat irregularly) 
denticulate dorsal edge; the right valve has the concentric sculpture more 
distant and ventrally, shows distinctly elevated narrow lines with wider 
interspaces regularly disposed, and also bears denticulations on its pos¬ 
terior dorsal margin; the umbones are nearly smooth; the shell gapes but 
little, chiefly at the end of the rostrum; internally the surface of the 
valves is smooth, the muscular and pallial impressions are brilliantly 
polished; besides the usual marks, in the specimen under examination 
there are, near the posterior ventral angle of the pallial sinus, two small 
circular impressions and some obscure and irregular markings at the 
entrance of the sinus, all due, doubtless, to attachments of the mantle and 
probably inconstant or variable in different individuals; the interior part 
of the pallial sinus nearly reaches the scar of the anterior adductor, and 
