95 



inflated, projecting above the dorsal margin ; anterior auricle small, beak-like, somewhat recurved 

 over the insinuated margin ; no distinct posterior auricle ; cardinal area narrow, long extending 

 to about Yg from the posterior margin; colour of shell shining white externally, with i6 — 18 thin 

 wavy stripes of a brown colour running from the dorsal to the ventral margin almost parallel 

 to one another, nacre bluish-green. 



Measurements (in millimètres). 



Holotype Paratype 



Length 21 17.5 



Height 1 1.4 1 1.2 



Maximum diameter . . 5.6 5.4 



Habitat : — Two shells of this very beautiful and highly fragile species were collected 

 by the „Siboga" Expédition in Buka or Cyrus Bay, east coast of Rotti Island (St. 299). 



Remarks : — This species, which I hâve associated with the name of my friend Mr. J. 

 R. Le B. Tomlin, appears to be allied to P. zébra (Reeve), but is distinguished by its shape, 

 texture and colouration. 



8. Pteria sibogae sp. nov. (Plate VIII, figs. 11, 12). 



The following is a description of this new species : — Shell small, thick, elongate ovate, 

 oblique, posteriorly produced into a narrow wing ; shell surface covered with low, concentric 

 ridges moderately inflated, maximum inflation just behind the umbonal région, curving down 

 gradually to the marginal areas ; dorsal margin long, almost straight ; anterior auricle short, 

 triangular, separated by a distinct notch for the byssus ; posterior auricle elongate, narrowing 

 down to a point at the tip ; posterior margin broadly concave ; anterior margin convex ; cardinal 

 area narrow, extending to the posterior auricle. Colour of shell dusky brown, auricles chestnut; 



nacre ligfht metallic blue. 



Measurements (in millimètres) 



Holotype Paratype 

 Length (including the auricles). . . 30 29 



Height 16.8 15 



Maximum diameter 7.5 7 



Habitat : — Three shells of this interesting species were collected at Buka or Cyrus Bay, 

 south coast of Rotti Island (St. 299), Anchorage east ofl^ Sailus Besar, Paternoster Islands (St. 315) 

 and l'/jj mile south of Tandjong Lajar, south coast of Bawean Island (St. 222). The Holotype 

 is from St. 222. 



Remarks : — Pteria sibogae is allied to P. chinensis (Leach), and P. aquatilis (Reeve), 

 but is distinguished by its shape and the peculiarly sharp and narrow auricles. 



Subgenus Electroma Stoliczka. 



1870. Electroma Stoliczka, Cretaceous Faun. S. India, Pelecypoda, p. 391. 



Stoliczka created this genus for Avicula-like forms with the valves more inequivalve 

 than in true Avicula {==■ Pteria)^ the right valve flatter, a short and almost edentulous hinge- 

 line, and a very short posterior wring not at ail separated from the body of the shell. 



