296 JOURNAL OF CONCHOLOGY, VOL. I5, NO. ID, SEPTEMBER, I918. 



ment pit, its funnel shaped siphon, as well as by its glossy, usually 

 strongly striate and alwaj's inappendiculate shell. 



P. subtruncatum Malm. Plate 7, figs. 1-4. 



A small, thickened and rather tumid form, with the umbones placed 

 close to the posterior end, is found in the canal. In this the short- 

 curved cardinals are quite unlike those of the common form of the 

 species, in which these teeth are very long and almost straight. It is 

 less abundant than the other species. 



P. tenuilineatum species nova. Plate 8, figs, i and 4-13. 



• Animal albesceiis ; siphojie magno, brevi. 



Testa oblongo-ovata. himidissima, valde incrassata, incequilateralis, 

 antice aliquantum prolongata, postice truncata, infra niagnopere 

 arcitata, regulariter striata ; umbones pronii?ie>ites, rottindati, 

 hand appendiadati ; cardo valde incrassatus ; denies laterales 

 validi, pariun elevati, niucronibus vix prominentibus. 



P. tenuilineatum differ t a F. parvulo, dente posteriore tertio (p. III.) 

 Tiec intro incurvato nee in primum (p. I.) ad umbonem versus 

 incidente, et siphone multo majore} 



Animal whitish ; siphon large, very short, orifice narrowly ellip- 

 tical, margin of the tube fringed and slightly reflected at its fullest 

 expansion ; foot very extensile, narrow and long. 



Shell small, about I'S x 1-4 x I'l mm., oblong oval, very tumid, 

 greatly thickened ; stri^ exceedingly regularly spaced and resembl- 

 ing carefully ruled lines ; umbones prominent, round, without 

 appendiculse, placed towards the posterior end ; dorsal margin 

 sloping quickly and about equally on both sides of the umbo, and 

 passing gradually into the anterior and posterior margins ; anterior 

 margin bluntly pointed ; posterior margin somewhat truncated ; 

 VENTRAL MARGIN curved ; hinge much thickened, with the interior 

 lateral teeth very strongly developed, and the interior outline of the 

 hinge-plate greatly arched ; teeth in the right valve : — c. 3 bent, 

 the posterior portion thickened and somewhat clavate ; a. I And p. I 

 almost at right angles to the axis of the hinge-plate under the umbo, 

 thickened and showing opaque lines of growth, cones sometimes 

 splayed inwards and only slightly conical; a. ///and/, ///upright 

 or leaning against the shell-wall, long and ridge-like, with the cones 

 scarcely developed ; teeth in the left valve : — c. 4 greatly curved ; 

 c. 2 leaning towards the umbo and sometimes almost prostrate — in 

 which case the upper surface is furrowed and it resembles c. 2 of 

 P. amnicum — dying away anteriorly in a low ridge, part of which 



^ I I have to thank Mr. J. R. le H. Toniliii foi- rendering this brief description into Latin. 



