i4 Bulletin 24 52 



by a calcareous deposit, terminating in siphonal tubes. 



Length 1^, height 6, thickness 5 mm, 



This species is quite different from the other described Mio- 

 cene Liothophagus. L. subalveatus Con. has a wide medial furrow 

 and obliquely produced posterior end. L. ionensis Glenn is charac- 

 terized by its broad posterior portion. L. yorkensis on the other 

 hand shows relations with the recent L. aristata Dillwyn, as indi- 

 cated above. In the case of the recent shell, the posterior extremi- 

 ty is twisted and attached to the calcareous shell which surrounds 

 it. The Miocene shell is perfectly loose as shown in figure 10, Plate 

 2. Conrad appears to have had a specimen of this species, as a 

 fair but characteristic figure is given on Plate 3, figure 1 of Kerr's 

 Rept., N. C. Geol, Survey but unaccompanied by either name or 

 description. 



Yorktown formation ; Yorktown {type) ; Bellefield, Va. 



Spisula (Hemimactra) harrisi, n. sp., Plate 1, Figs 5, 6 



Shell large, thin, subtrigonal in shape ; beak narrow and 

 pointed, markedly curved anteriorly, over the impressed anterior 

 submargin ; anterior end slightly longer than the posterior, anter- 

 ior submargin dorsally impressed and flattened, becoming depress- 

 ed near the basal margin ; posterior dorsal margin impressed and 

 flattened its entire length and with a furrow extending from un- 

 derneath the beak, and becoming rapidly obsolete and terminating 

 at about one-half of the distance along the dorsal margin measured 

 from the beak ; surface smooth, on the center of the shell disk, 

 very irregular with growth lines along the basal margin ; a fine 

 longitudinal line along the angle bounding the impressed postero- 

 dorsal submargin ; on the dorsal side of this line the growth lines 

 are very coarse, becoming smooth again on the furrow ; hinge 

 agreeing with that of .S. curtidens Dall, but slightly less heavy. 



Height 105, width 122, thickness 4.2 mm. 



This species is closely related to 5\ curtidens Dall. Compari- 

 sion with Dall's type in the National Museum however shows 

 that the species is distinct. These differences may be noted. S. har- 

 risi is slightly less heavy, the dorsal submargins are more 



