256 AXEL A. OLSSON 



riblets between wider interspaces, the whole finely reticulated by concentrics, 

 the radials generally weak on the anterior part of the shell and can be ob- 

 served only by magnification. The posterior area is sculptured by well- 

 developed radials crossed by a few, widely spaced concentric laminae. A 

 large specimen measured by Hertlein and Strong measures: length 46.8 mm., 

 height 38,7 mm. 



L. annettae appears to be a more northerly species differing from 

 L. cumingii by its paler color, higher, broader shell, and shorter posterior 

 side which is also more strongly sculptured. 



Range — Mexico to Costa Rica. 



Subfamily LAETICARDIENAE 

 Genus LAEVICARDIUM Swainson, 1840 

 Type species by subsequent designation, Stoliczka, 1871, Cardium 

 oblongum Gmelin. 



Shell ovate to obliquely subovate, convex, equivalve, with wide um- 

 bones and small, adjacent beaks, moderately thin. Surface often smooth and 

 poHshed, sometimes with numerous, low, obvious to indistinct, radial riblets, 

 due mainly to a radial structural characteristic of the inner layer and show- 

 ing more plainly as sharp serrations or crenulations along the ventral mar- 

 gin. Dorsal areas well marked, differentiated principally by their plain sur- 

 face, without radial riblets and simple, uncrenulated margins. Hinge with 

 a single large cardinal tooth and socket in each valve, the right valve with 

 a small anterior cardinal immediately above the deep cardinal socket; lateral 

 teeth and sockets are equidistant and strong in each valve. Ligament ex- 

 ternal, seated above and behind a flat nymphal plate. Color white or yellow, 

 often rayed and mottled. Periostracum thin, deciduous. 



LaeTicardimn (LaeTicardium) elenense (Sowerby) Plate 38, figures 2, 2a 



Cardium elenense Sowerby 1840, Conch. Illust., Cardium, p. 6, No. 73, fig. 58. — Sowerby, 



1841, Proc. Zool. Soc. London for 1840, p. 109. — ^Reeve, 1845, Conch. Icon., vol. 



2, Cardium, pi. 20, fig. 104. 

 Cardium (Laevicardium) elenense Sowerby, Hertlein and Strong, 1947, Zoologica, vol. 



31, No. 4, pp. 145, 146. — Hertlein and Strong, 1955, Bull. Amer. Mus. Nat. Hist., 



vol. 107, art. 2, p. 187. 



The shell is generally small (less than 20 mm., high), obliquely sub- 

 ovate, the posterior-dorsal slope narrowly flattened, its margin straight. 

 Surface smooth, polished, but weakly rayed. Color white but more often 

 mottled with brown or purple, sometimes in irregular streaks or in wavy 

 bands, the interior usually brown. Narrow concentric bands are often present 

 on the umbones. Strength of the radial ribbing is variable. 



Length 15 mm., height 15.3 mm., diameter 9.6 mm. Esmeraldas, 

 Ecuador. 



Range — ^Gulf of California to northern Peru. Panama: Pearl Islands, 

 Ecuador: Santa Elena; Manta; Esmeraldas. Peru: Zorritos; Mancora. 



Laeylcardiam (LaevlcardJum) elenense aplciiinm Carpenter 



LaeTicardium apicinum Carpenter, 1864, Annals Mag. Nat. Hist., scr. 3, vol. 13, p. 313. 

 Cardium {Laevicardium) elenense apicinum (Carpenter), Hertlein and Strong, 1947, 

 Zoologica, vol. 31, pt. 4, p. 146. 



