DALL: MOLLUSCA AND BRACHIOPODA. 427 
U.S.S. “ Albatross,” station 3034, off Point Fermin, at the head of the Gulf 
of California, in 24 fathoms, mud, bottom temperature 63°.5 F. U.S. N. Mus. 
110,548. 
This differs from P. discus Stearns, in the radial arrangement and larger size 
of its ‘surface granules, its wider rostrum, and more compressed form. It needs 
no comparison with other species. 
HALISTREPTA Dat. 
Halistrepta Dall, Nautilus, March, 1904, 17, p. 123; type, Periploma sulcata Dall. 
Periploma (Halistrepta) sulcata Datt. 
Plate 15, figure 10. 
Periploma sulcata Dall, Nautilus, March, 1904, 17, p. 122. 
San Pedro, California, on the beach; collected by Mrs. Oldroyd. 
I take this opportunity of illustrating this rare, interesting, and unfigured 
species. 
Lyonsudae. 
LYONSEA Turton. 
Lyonsia panamensis Da tt, n. sp. 
Plate 18, figure 12. 
Shell thin, slightly inequivalve, inequilateral, subquadrate, translucent whitish, 
with a very thin greenish-gray periostracum ; beaks large, full, somewhat anterior, 
prosogyrate ; no lunule or escutcheon ; anterior end short, rounded, anterior dorsal 
slope rapidly descending ; posterior dorsal slope more horizontal and longer ; poste- 
rior end subtruncately rounded ; base gently arcuate; surface covered with radi- 
ating close lines of granules, of which about every fourth line is more prominent 
than the others; numerous fine sand grains are adherent to the surface ; interior 
perlaceous, finely radiately striate; scars conspicuous, the anterior larger; pallial 
sinus wide, shallow; hinge feeble, a single obscure tooth and short nymph in the 
right valve; ligament feeble, almost internal. Lon. 13.5; beaks behind anterior 
end, 6.5; alt. 10.0; diam. of right valve, 4.5 mm. 
U. 8.58. “ Albatross,” station 4630, Gulf of Panama, Mariato Point N. 
70° EH. fifty-one miles, in 556 fathoms, sand, bottom temperature 40°.5 F. 
U.S. N. Mus. 110,584. 
Only the right valve was obtained. 
