Mollusca of the Arabian Sea, (&c. 99 



Hob. Near Karachi and also Malcolm Inlet, Persian Gulf, 

 24 fathoms. 



A remarkably delicate, semitransparent, milky-white shell, 

 slightly inequilateral, entirely concentrically laminated with 

 about sixty close-lying ridges ; these are very thin and worn 

 off, as a rule, towards the umbones ; these last are contiguous, 

 curving anteriorly ; there is a longitudinal oblique conspicuous 

 fold or groove, extending posteriorly from the umbo to the 

 hinder extremity, and likewise in front ; a distinct lunule ; 

 the dorsal margin of the shell is serrate or fimbriolate ; in 

 juvenile examples the lamellae are more sparse and distant, 

 but the serrations are conspicuous and seem to extend far 

 down both sides almost to the ventral margin. As is the 

 case with several allies, e. g. L. pennsylvanica, L., L.jamat- 

 censi's, Lamk., small pellucid raised dots are noticeable with 

 a lens on holding up a specimen to the light. 



Several examples, but mostly single valves, only one being 

 quite perfect, and that in young condition, with fewer con- 

 centric lamellse (fig. 9 a). 



Diplodonta holosphcera *, sp. n. (PI. II. fig. 11.) 



D. testa rotundato-circulari, alba, parum nitida, plana, tumida, 

 sequivalvi, ut proxime tequilaterali; umbonibus contiguis, margine 

 dorsali antice pauUulura excavate, postice leniter obliquo, deinde 

 omnino rotundato, Hgamento externo ; valva sinistra duobus 

 dentibus cardinalibus approximatis, dextra duobus, postico bifido ; 

 superficie intus alba, pellucente ; linea palliali simplici. 



Alt. 8j lat. 8-50, diam. 7'oO mm. 



Hah. At very low tides, Karachi ; also imbedded in rocks 

 at 40 fathoms, lat. 27° N., long. 52" E., Persian Gulf. 



A few examples of an almost circular sphseroid Diplodonta ; 

 valves as nearly as possible equilateral, the umbones con- 

 tiguous, ligament external, margin on either side of the 

 umbones very slightly excavate anteriorly, obliquely straight 

 posteriorly for a short distance, then completely round ; the 

 body of the shell very tumid ; there are in either valve two 

 teeth, those of the left valve are closely approximate, the 

 pallial line being simple. 



Scintilla callipareia f, sp. n. (PI. II. fig. 10.) 



S. testa vitrea, delicata, oblongo-ovata, ajquivalvi, semiclausa, ftre 

 ^quilaterali, nitida, la;vi, palHde rosea; umbonibus contiguis, 



* oXof, complete, <r0aipa, a globe. 

 t KakXinaprjos, beautiful cheeked. 



