PANAMIC-PACIFIC PELECYPODA 101 



by the ligament. Hinge teeth divided into two series, the anterior set being 

 short and irregular, the posterior set much longer, regular. Tip of the beak 

 often stained with black. 



Lnnarca brerifrons (Sowerby) Plate 8, figures 7, 7a-7c 



Area brevifrons Sowerby, 1833, Proc. Zool. Soc. London, p. 22. — Reeve, 1844, Conch. 



Icon., vol. 2, Area, pi. 1, fig. 6. 

 Scapharea (Argina) brevifrons (Sowerby), Maury, 1922, Paleont. Amer., vol. 1, pt. 4, 



p. 200. 

 Argina brevifrons variety buearuana Sheldon and Maury, 1922, op. eit., pp. 200, 201, 



pi. 2, fig. 16; pi. 3, fig. 10. 

 Lunarca brevifrons subsp. brevifrons (Sowerby), Reinhart, 1943, Special Paper, Geol. 



Soc. America, No. 47, p. 75. 

 Lunarca brevifrons subsp. buearuana (Sheldon and Maury), Reinhart, 1943, op. cit., 



p. 75, pi. 7, figs. 5-7. 

 Area (Argina) vespertina Morch, 1861, Malak. Blatter, vol. 7, p. 204. 

 Lunarea vespertina (Morch), Rost, 1955, Allan Hancock Pacific Expeditions, vol. 20, 



No. 2, pp. 209, 210, pi. 15, figs. 24 a-b; text-figs. 93 a-c. 



The count of 22 or 23 ribs as given by Reeve for this species is incorrect 

 as the type examined in the British Museum has 35 ribs in the left valve. 

 All our specimens of L. brevifrons from Peru have 30 or more ribs. Area 

 (Argina) vespertina Morch and Area (Barbatia?) melanoderma Pilsbry 

 and Lowe are forms of L. brevifrons. The beak is commonly stained with a 

 black streak. 



Range — Lower California to northern Peru. Panama: Old Panama; San 

 Carlos; Biicaro. Ecuador: Mompiche; Galeras; Manta; Santa Elena. Peru: 

 Tumbez; Zorritos; Punta Picos; Mancora; Negritos. 



Subfamily NOETDfAE 



Genus NOETIA Gray, 1857 



Type species by monotypy, Noetia triangularis Gray = N. reversa 

 (Sowerby). Recent, Panama-Pacific province. 



Shell subrhomboidal to subtrigonal, its posterior side flattened or im- 

 pressed, its end pointed or produced. Beaks opisthogyrate, varying in posi- 

 tion from nearly central to strongly posterior. Cardinal area high or narrow, 

 covered by the ligament, and vertically grooved or striated, the ligament 

 largely or wholly confined to the anterior side. Adductor scars large and 

 distinct, the posterior one usually with a raised edge or flange below. 

 Surface covered with a dense, scaly to pilose periostracum. 



Noetia (Noetia) reversa (Sowerby) Plate 10, figures 1, la, lb 



Area reversa Sowerby, 1833, Proc. Zool. Soc. London, p. 20. Tumbez, Peru.— Reeve, 



1843, Conch. Icon., vol. 2, Area, pi. 1, fig. 5 

 Noetia reversa (Gray), Sowerby, Maury, 1922, Paleont. Amer., vol. 1, No. 4, p. 171, 



pi. 1, figs. 7, 11. 

 Noetia reversa (Sowerby), H. and A. Adams, MacNeil, 1938, Prof. Paper 189-A, U. S. 



Geol. Survey, pp. 38, 39, pi. 6, figs. 7, 22, 23. 

 Noetia (Noetia) reversa (Sowerby), Reinhart, 1943, Special Paper, Geol. Soc. America, 



No. 47, p. 77, pi. 14, figs. 5, 7, 8.— Hertlein and Strong, 1943, Zoologica, vol. 



28, pt. 3, p. 163.— Rost, 1955, Allan Hancock Pacific Expeditions, vol. 20, No. 



2, p. 211, text-figs. 94 a-c. 

 Area Hemicardium Koch in Philippi, 1843, Abbild. und Beschreib. Conchylien, vol. 1, 



p. 43, Area, Tafel 1, fig. 1. 

 Noetia triangularis Gray, 1857, Annals Mag. Nat. Hist, 2d ser., vol. 19. p. 371. 



Shell of medium size (largest about 50 mm.), convex and solid. Pos- 

 terior side short, sharply truncated, usually flat, its margin straight, occa- 



