PANAMIC-PACIFIC PELECYPODA 109 



and beaks with a strong posterior curve, opisthogyrate, with the larger 

 portion of the cardinal area lying on the anterior side. Ribs through the 

 middle zone of the disk are large and relatively few in number (6 to 10) 

 fading out on the appressed submargins into cord or threadlike radials. 

 Two species. 



Key to species Axinactis 



I. Ribs relatively few (about 6), large in the middle, the valves convex 

 with appressed submargins. 



G. inaequalis 



II. Ribs more numerous (about 10), valves rounder. 



G. delessertii 



Axinactis inaequalis (Sowerby) Plate 11, figures 8, 8a, 8b 



Pectunculus inaequalis Sowerby, 1832, Proc. Zool. Soc. London, p. 196. — Reeve, 1843, 

 Conch. Icon., vol. 1, Pectunculus, pi. 4, fig. 16 Bay of Panama and Real Llejos. 



Pectunculus assimilis Sowerby, 1832, Proc. Zool. Soc. London, p. 196 dredged in sandy 

 mud and gravel, in from eight to twelve fathoms at Puerto Portrero and in 

 the Bay of Guayaquil. — Reeve, 1843, op. cit., pi. 4, fig. 15. 



Glycymeris inaequalis (Sowerby), Hertlein and Strong, 1943, Zoologica, vol. 28, pt. 2, 

 p. 153. 



Shell coarse, obliquely trigonal to flatly cardiform, the umbones strongly 

 curved posteriorly. Beaks small, opisthogyrate, with the cardinal area lying 

 almost wholly on the anterior side of the beaks. Ribs in the middle zone 

 of the valve large, few (six or seven) becoming small on the submargins 

 or replaced there by the strong longitudinal threads which overrun them. 

 Hinge teeth in an arch, large and relatively few in number. Color sometimes 

 nearly white but generally with a pattern of transverse, zigzag brown bands, 

 closely or widely spaced. 



Length 40.3 mm., height 44.4 mm., diameter 30 mm. 



Punta Mambri, Ecuador. 



Range — Gulf of California to northern Peru. Panama: Panama City; 

 Pearl Islands; Burica Peninsula. Canal Zone: Venado Beach. Ecuador: 

 Esmeraldas; Limones; Manta; Isla la Plata; Santa Elena; Punta Mambri. 

 Peru: Zorritos; Mancora; Sechura. 



Axinactis delessertii (Reeve) Plate 11, figures 7, 7a 



Pectunculus delessertii Reeve, 1843, Conch. Icon., vol. 1, Pectunculus, pi. 9, fig. 52. 



Hab — / Reeve, 1843, Proc. Zool. Soc. London, p. 190. 

 Glycymeris (Axinactis) delessertii (Reeve), Hertlein and Strong, 1943, Zoologica, vol. 



28, pt. 3, p. 153. 



Shell like A. inaequalis but larger, rounded, the ribs more numerous. 

 Interior white stained with brown on the posterior side. 



Range — Mexico to Panama. Mexico: Tres Marias Is. (ANSP 160732. 

 H. N. Lowe). Panama: Panama. (ANSP 7953. T. B. Wilson). 



Family LIMOPSIDAE 



The shell is small or of medium size, glycymerid in shape, sometimes 

 nearly symetrically rounded or trigonal, or strongly obliquely suborbicular, 

 the anterior side then shorter than the other, equivalve. Umbones are sub- 

 central with the beaks rising a Httle above the hinge and cardinal area. 



