PANAMIC-PACIFIC PELECYPODA 347 



Iphigenta altior Sowerby, Dall, 1909, Proc. U.S. Nat. Museum, vol. 37, No. 1704, pp. 

 159, 274, pi. 25, fig. 8.— Hertlein and Strong, 1949, Zoologica, vol. 34, pt. 

 4, p. 257. 



Shell of medium or large size (length to about 70 mm.), subtrigonal, 

 the umbones nearly central, solid and porcellaneous. Fresh shells have a 

 straw-colored to dark-brown periostracum, beneath it the shell is porcel- 

 laneous white or tinted with reddish violet or deeper purple. 



Length 70 mm., height SO mm., diameter 35 mm. 



This species is similar to /. brasUiensis Lamarck of the Caribbean and 

 West Atlantic but in general /. altior has a higher shell with the beaks more 

 nearly central, and the posterior-ventral indentation is generally not so 

 marked as in the Caribbean shell. 



Range — Gulf of California to northern Peru. Costa Rica: Gulf of 

 Nicoya. Panama: Bucaro; San Carlos; Puerto Chama; Viveros Island 

 (Pearl Islands). Colombia: Isla del Gallo; Tumaco. Ecuador: Santa Elena; 

 Palmar; Manta; Charapota. Peru: Tumbez; Bayovar. 



Family SANGUmOLARIlDAE 



(Psammobiidae or Gariidae) 



The shell is telliniform, donaciform, or soleniform, usually equivalve 

 and if unequal, the right valve is the larger and more convex, usually with 

 a gap at the posterior end. The surface is often highly colored in which 

 shades of red, pink, and purple predominate, spread uniformly or in a 

 streaked, maculated, or rayed pattern. The hinge has one or two, bifid or 

 grooved cardinal teeth; there are no laterals. The ligament is external, large, 

 lies entirely posterior of the beaks and is attached to a large, nymphal 

 plate which rises prominently above the hinge margin. The adductor scars 

 are distinct, placed rather high dorsally and connected by a pallial line 

 bearing a deep sinus. The periostracum is usually coarse and dark in color 

 in some groups, thin and inconspicuous in others. 



This family differs from the Tellinidae mainly on anatomical' grounds 

 and in the more perfect adaptation of its species to a burrowing habit. In 

 the typical species, the shell has a large, open, posterior gap; in the genus 

 Heterodonax, there is no gap, the margins of the valves fitting closely. The 

 species show much diversity in shell form and sculpture but the Panamic 

 species are mostly smooth: in Asaphis of the Caribbean, the surface is finely 

 ribbed. In key form, the Panamic genera are arranged as follows: 



I. No posterior gap, the margins of the valves closing tightly all around. 



1. Shape subcircular, soHd, and with concentric sculpture. 



Genus Heterodonax 

 II. Valve margins not closing tightly but with an open space or gap at 



the posterior end. 

 A. Shell razor-like in shape, elongated, the dorsal and ventral margins 



straight, and nearly parallel. The beaks and umbones are near the 



middle. 



2. Surface of the valves plain, marked with concentric growth lines only. 

 Color white or flushed irregularly with violet. 



Genus Tagelus 



