MAEYLA-JSTD GEOLOGICAL SUKVEY 355 



Length, 27.5 mm.; height, 23.5 mm.; diameter, 6 mm. 



Occurrence. — Choptank Foemation. Governor Eim (upper bed), 2 

 miles south of Governor Eim (upper bed), Flag Pond (upper bed), Tur- 

 ner, Dover Bridge, Peach Blossom Creek, Trappe Landing, Sand Hill. 



Collections. — Maryland Geological Survey, Johns Hopkins University, 

 Academy of Natural Sciences of Philadelphia. 



ASTAETE THISPHILA U. sp. 



Plate XCIV, Figs. 7, S, 9. 



Astarte undulata Conrad, 1S42, Proc. Nat. Inst., Bull, ii, p. 185 (listed only); not of 



Say, 1824. 

 Astarte undulata Conrad, 1867, Proc. Acad. Xat. Sci. Phila., vol. xix, p. 139 (listed 



only). 

 Astarte obrufa var. Harris, 1893, Amer. Jour. Sci., ser. iii, vol. xlv, pp. 26, 27 (listed 



only). 

 Astarte (Ashtarotha) undulata Dall, 1903, Trans. Wagner Free Inst. Sci., vol. iii, pt. 



vi, p. 1491 (in part). 



Description. — Shell triangular; moderately thick, convex, but de- 

 pressed or flattened near the beak ; angular undulations on the beak promi- 

 nent, becoming broader farther from the beak and extending well toward, 

 or in some cases entirely to, the basal margin ; tip of beak curved forward, 

 producing a convex curve or shoulder on the dorsal margin just posterior 

 to the apex; anterior margin regularly rounded; basal margin rounded 

 anteriorly, straight or slightly emarginate posteriorly ; posterior extremity 

 above the line of the base and obtusely rounded; interior smooth except 

 in quite young specimens, when it is sometimes slightly undulated ; teeth 

 strong. 



This species is quite common at the horizon of yellowish sands so well 

 exposed at Jones Wharf and has often been listed as A. undulata or as 

 A. ohruta, or A. ohruta var. It differs from A. undulata Say by being 

 usually less convex, by having coarser, broader undulations and a greater 

 flattening near the beak, by being much less variable in its proportion of 

 length to height — the height being less than the length while in undulata 

 it is often greater — and by having a much more curved basal margin than 

 the undulata. 



It differs from the A. ohruta by having a less symmetrically curved sur- 

 face and outline, l)y being strongly undulated and by the characteristic 



