240 AXEL A. OLSSON 



Solecardia peruviana, new species Plate 36, figures 3, 3a 



The shell is small, elongate-oblong, the umbone placed a little anterior 

 of the middle, the beak prosogyrate. Dorsal and ventral margins are nearly 

 parallel and straight with the two ends equal and rounded. The embryonic 

 shell is large and covers much of the beak. The hinge of the left valve has 

 two anterior cardinal teeth; behind them is a linear pit for the ligament 

 and on the margin behind it is a small posterior tooth. The sculpture con- 

 sists of flattened, smooth concentrics and small fimbriated radials towards 

 the basal margin and on the two ends, the riblets spreading out fan-shaped 

 upward. Internal margin smooth but with the furrows of the external radials 

 showing along both the anterior and posterior ends. There is no ventral gap. 



Length 4.8 mm., height 2.7 mm. a left valve. Zorritos, Peru. Holotype, 

 ANSP 218891. 



The surface sculpture recalls that of some species of Galeomma, but 

 the ventral margin is straight without any indication of an open gap. 

 Range — Peru. Peru: Zorritos. 



Genus TRYPHOMYAX, new genus 

 Type species, Tryphomyax lepidoformis, new species. Panama. 



The shell is small, thin, flat, scalelike, suboyate, its posterior side some- 

 what longer. The prodissoconch is a small or minute, brown cap on the tip 

 of the beak, and contrasts sharply with the pale white or translucent color 

 of the adult shell. The middle of the disk of both valves is crossed by a 

 narrow, vertical line or sulcus which at the ventral margin ends in a narrow, 

 deep notch. The surface is sculptured with low, radial riblets which as they 

 approach the dorsal margin fan out slightly at the ends; the riblets are finely 

 cancellated or shagreened by minutely waved concentrics. The hinge of the 

 right valve has a knoblike cardinal tooth in the middle; the left valve has 

 two cardinal teeth, of which the anterior one is the larger. The ligament is 

 internal, the resilifer small, placed behind the cardinal teeth. The hinge of 

 the right valve has a small, narrow tooth along its posterior-lateral margin. 

 The pallial line is entire, its course waved and situated well within the cavity 

 of the valve. 



Leiochasmea Dall, Bartsch, and Rehder, 1938 (type species, L. chascax 

 Pilsbry) from Hawaii is perhaps a related genus but has an edentulous 

 hinge, smooth surface without a ventral notch. The presence or absence of 

 the ventral notch is probably not an important character; it is extremely 

 well developed in T. lepidoformis, the type species, but is lacking in its sub- 

 species laevis. Vasconiella Dall, 1899, has its ventral notch restricted to the 

 much smaller, right valve as recently demonstrated by Kisch. 



Tryphomyax lepidoformis, new species Plate 36, figures 4, 4a 



The shell is small, flat, with the characters described for the genus. The 

 holotype is a left valve; this specimen has the central sulcus placed a little 

 in front of the middle, hence dividing the disk into two unequal parts, the 

 anterior section is the widest and highest, the sulcus forms a deep cut or 

 notch in the ventral margin. Sculpture formed by low, flat riblets, at first 

 simple but towards the ventral margin become double; the riblets are 

 minutely crenulated by fine concentric lines. The surface of the umbone 

 smooth. 



Length 4.1 mm., height 2.5 mm. Holotype, ANSP 218922. 



