PANAMIC-PACIFIC PELECYPODA 241 



So far, this interesting species is known only by eight free valves. A 

 single specimen of another form has no median sulcus and the surface is 

 nearly smooth. To this smooth form, the subspecific name "laevis" is pro- 

 posed, however, additional specimens may show that it should be considered 

 as a related but distinct species. T. lepidoformis laevis, new subspecies 

 (Plate 36, figures 7-7b). Holotype, ANSP 218923. 



Range — Panama. Panama: In beach drift, Lagartillo, near Las Tablas; 

 also attached to worm tubes. 



Family SPORTELLIDAE 



Shells are generally small, ovate to narrowly elongate, thin and usually 

 white in color. The umbones are usually prominent, sometimes near the 

 middle, or much closer to the anterior end. Hinge generally with one or 

 two large teeth in each valve. Ligament largely external, occasionally 

 showing a small, internal resilium. Surface smooth or roughened with 

 growth threads, sometimes heavily pustulated. 



Genus ENSITELLOPS Olsson and Harbison, 1953 



Type species by original designation, Sportella protexta Conrad. Mio- 

 cene of Virginia. 



Shell small, thin, solenoid, the anterior side much shorter than the 

 posterior, the dorsal and ventral margins straight and nearly parallel. The 

 protodissoconch is small but distinct, generally placed obliquely to the longer 

 axis of the mature shell. General surface is white, often earthy and with a 

 scattering of small spinelike pustules. In the left valve, the hinge has two 

 small, divergent anterior cardinal teeth, the right valve with one only. The 

 left valve has a long, slender, posterior tooth partly united with the nymph; 

 it fits into a grooved socket in the dorsal margin of the opposite valve. 



A genus of small, Solen-Vike shells common in the Miocene and Phocene 

 of the southeastern United States. 



EnsifHlops pacifica, new species Plate 80, figures 9, 9a 



Shell elongate, soleniform, the beak capped by the small, glossy prodis- 

 soconch placed near the anterior one-fourth or one-fifth. Valves unequal in 

 the degree of inflation, either the right or left valve is cylindrically convex, 

 the opposite valve is irregularly depressed, often strongly warped, the two 

 ends flexed inward as if to effect the closure of an otherwise gaping shell. 

 Color subtranslucent or milky white, marked with fine lines of growth, 

 and smooth or with a sprinkling of small pustules on the flatter valve. 

 Interior with the adductor scars indistinct, connected by an irregular pallial 

 line placed rather high, the cavity of the beak showing in the inside surface 

 of the prodissoconch in the semblance of a small pit. Hinge teeth small. 



Length 5 mm., height 2.8 mm., more convex valve, right valve. 



Length 5.4 mm., height 2.5 mm., a flatter valve with pustules, right 

 valve. 



Holotype, ANSP 218893; paratype, ANSP 218894. 



This species is moderately common at El Lagartillo near Las Tablas, 

 Panama. It is related to E. protexta (Conrad) first described from the 

 Miocene of Virginia but now also known to occur in the Recent along the 

 southeast coast of the United States. 



