DALL : Ml iLLUSCA AND BRACHIOPODA. 427 



U. S. S. " Albatross," station 3034, off Point Fermin, at tlie head of the Gulf 

 of California, in 2i fathoms, mud, bottom temperature 63°. 5 F. U. S. N. Mus. 

 110,548. 



This differs from P. discus Stearns, in tlie radial arrangement and larger size 

 of its surface granules, its wider rostrum, and more compressed form. It needs 

 no comparison with other species. 



HALISTREPTA Dall. 

 Halistrepta Dall, Nautilus, March, 1904, 17, p. 123 ; type, Periploma sulcata Dall. 



Periploma (Halistrepta) sulcata Dall. 



Plate 15, figure 10. 



Periploma sulcata Dall, Nautilus, March, 1904, 17, p. 122. 



San Pedro, California, on the beach ; collected bj Mrs. Oldroyd. 

 I take this opportunity of illustrating this rare, interesting, and uufigured 

 species. 



Zi/onsridae. 



LYO'SIA TuRTox. 



Lyonsia panamensis Dall, n. sp. 



Plate 18, flsiire 13. 



Shell thin, sliglitly iucquivalve, inequilateral, subquadrate, translucent whitish, 

 with a very thin greenish-gray periostracuin ; 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, tlie anterior larger; pallial 

 sinus wide, shallow; hinge feeble, a single obscure tooth and short nymph in the 

 riglit valve; ligament feeble, almost internal. Lon. 13..5 ; beaks behind anterior 

 end, 6.5 ; alt. 100 ; diam. of riglit valve, 4.5 mm. 



U. S. S. "Albatross," station 4630, Gulf of Panama, Mariato Point N. 

 70° E. fifty-one miles, in 556 fathoms, sand, bottom temperature 40°.5 F. 

 U. S. N. Mus. 110.584. 



Onlv the right valve was obtained. 



