52 AXEL A. OLSSON 



SYSTEMATIC TREATMENT 



Subclass PROTOBRANCHIA 



Order PALAEOCONCHA 



Superfamily SOLEMTACEA 



Family SOLElkfYIDAE 



The shell is elongate, soleniform, thin or moderately thick, equivalve 

 and gaping widely at both ends, the dorsal and ventral margins straight 

 and parallel, the anterior side longer, the surface covered by a glossy, brown 

 to black periostracum extending beyond the free margins of the valve as 

 conspicuous, frill-like laps. Hinge margin without teeth, the ligament internal 

 or partly external. Pallial impressions usually weak, the posterior adductor 

 scar bordered in front by a thickened ray. Surface smooth, plain, or radially 

 rayed. 



Genus S0LE3IYA Lamarck, 1818 



Type species by subsequent designation, "Solenomya" mediterranea 

 Lamarck (=Solemya mediterranea Lamarck =Tellina togata Poli, 1791) 

 (see Vokes, 1955, Jour. Paleont., vol. 29, No. 3, p. 534). 



With the characters of the family. The genus is divided by Dall into 

 three subgenera as follows: 



L Ligament amphidectic, along both sides of the beak, chiefly internal, 

 in advance of the chondrophore. 



Subgenus Solemya, s. s. 

 II. Ligament opisthodetic, internal, not exposed in front of the chondro- 

 phore. 



Subgenus Petrasma 

 IIL Ligament opisthodetic, wholly internal, visible internally only where 

 it crosses the gap between the valves. 



Subgenus Acharax 



The genus Soletnya comprises relatively rare shells, seldom collected 

 except by dredging, the fragile shell being easily damaged by drying out, 

 the periostracum becoming separated from the layer beneath. Most species 

 are deepwater but one form, S. (Petrasma) panamensis may sometimes be 

 encountered on mud flats at extreme low water. Solemya is known by 

 several fossil species in the Oligocene and Miocene of Peru, Ecuador, Colom- 

 bia, and Panama. 



Subgenus ACHARAX Dall, 1908 



Type species by original designation, S. johnsoni Dall. 

 Solemya (Acharax) johnsoni Dall Plate 1, figure 5 



Solemya johnsoni Dall, 1891, Proc. U. S. Nat. Museum, vol. 1+, p. 189.— Dall, 1895, op. 



cit.. vol. 17, p. 712, pi. 25, fig. 1. 

 Solemya (Acharax) johnsoni Dall, Hertlein and Strong, 1940, Zoologica, vol. 25, pt. 4, 



p. 376.— Maxwell Smith, 1944, Panamic Marine Shells, p. 47, fig. 612. 

 Solemya (Acharax) agassizii Dall, 1908, Bull. Mus. Comp. Zool., vol. 43. No. 6, p. 365, 



pi. 16, fig. rO.— Hertlein and Strong, 1940. op. cit., pp. 375, 376.— Maxwell Smith, 



1944, op. cit., p. 47, fig. 613. 

 Solemya (Acharax) johnsoni Dall and S. (A.) agassizii Dall, Vokes, 1955, Jour. Paleont., 



vol. 29, No. 3, p. 538. 



This is a deepwater species with valves reaching a length of 150 mm.. 



