PANAMIC-PACIFIC PELECYPODA 191 



prominent, cup-shaped, smooth embryonic shell or an enlarged prodissoconch 

 surrounded by a raised ledge or rim. Hinge plate stout, with a submedian 

 resilifer pit bordered by stubby or hook-shaped cardinal teeth and the 

 anterior and posterior lateial margins with distant teeth and sockets. Ex- 

 ternal sculpture formed by coarsely noded, curved, radial riblets. 



C'ondjlocardia panamenslg Olsson Plate 77, figure 4 



Condylocardia panamensis Olsson, 1942, Bulls. Amer. Paleont., vol. 27, No. 106, pp. 186 

 187, pi. 3, figs. 9, 10. 



Shell minute, generally glassy and solid, equivalve, but strongly in- 

 equilateral. Externally, the valves are broadly subtrigonal, the posterior 

 side produced and somewhat pointed with a large, excavated escutcheon- 

 like area. Umbones prominent, surmounted by a platelike, smooth, prodis- 

 soconch encircled by a thickened raised margin. External sculpture con- 

 sists of a few, strong, radial riblets, largest in the middle zone, smaller on 

 the sides and nearly absent from the posterior extremity; on a normal shell, 

 these ribs number about eight. Spaces between the ribs are wide, traversely 

 grooved or striated by the lines of growth. Hinge: the right valve has a 

 strong, knob or hook-shaped anterior cardinal tooth and a socket for the 

 left posterior cardinal tooth and between these is the attachment pit for 

 the resilium. There is also a large anterior lateral tooth and a smaller 

 posterior lateral tooth. Shell cavity deep, the ventral margins deeply fluted 

 by the ends of the ribs which show through the glassy or translucent text- 

 ture of the shell. Average length about 1.75 mm. 



Common as a Pleistocene fossil on the Burica Peninsula, Panama, but 

 only a few Recent specimens have so far been collected. Recent specimens 

 are white or rose-colored. The Pacific shell is closely related to C. bernardi 

 Dall and C. smithii Dall from the Caribbean and West Indian waters. 



Range — Panama. Panama: Bucaro. 



Superfamily SPHAEBICEA 

 Family COKBICULIDAE 



Brackish or marine clams of medium or large size, ovate-trigonal or 

 rounded shape and of medium or solid texture. Fresh shells are covered 

 with a coarse yellow, green or dark-brown periostracum as a protection 

 against corrosion, often deeply worn off the umbones and beaks, the surface 

 of the shell underneath white or flushed irregularly with purple and marked 

 with fine growth line striae or stronger concentrics. The ligament is ex- 

 ternal, attached to a nymphal plate, the opposing surface of which may be 

 smooth or rugose. Hinge with three cardinal teeth in each valve (some of 

 which may be bifid) and both anterior and posterior lateral teeth, the 

 lateral teeth being smooth or striate. No lunule or escutcheon. Pallial line 

 entire or sinuate. 



Although some species of Panamic-Pacific corbiculids are locally 

 gathered as a seafood, their shells are but sparingly represented in museum 

 collections and the range and variation of some species is not well under- 

 stood. The Panamic species have been greatly overnamed but the status 

 of many of these forms must await the availability of larger and more 

 complete collections. 



