520 Systematic Paleontology 



Yoldia gabbana (Whitfield) 



Leda protexta Gabb, 1860, Jour. Acad. Nat. Sci., Phila., 2d ser., vol. iv, p. 



397, pi. lxviii, fig. 36. (Not L. protexta Gabb, Jour. Acad. Nat. Sci., 



Phila., 2d ser., vol. iv, p. 303, pi. xlviii, fig. 23.) 

 Nuculana gabbana Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 106, 



pi. xi, figs. 11-13. 

 Leda gabbana Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, p. 378, 



pi. xxix, figs. 28-30. 



Description. — " Shell of moderate size, extremely elongated, the length 

 being nearly twice and a half the extreme height. Valves convex, regu- 

 larly and evenly rounded. Beaks small, appressed and incurved, and dis- 

 tinctly inclined toward the narrower end of the shell, scarcely rising above 

 the hinge line on the wider part, and situated about two-fifths of the length 

 from the larger end. Cardinal margin on the wider end gently arcuate 

 and a little more strongly concave on the narrower side of the beak ; large 

 extremity of the shell sharply rounded ; basal margin gently rounded 

 throughout and the posterior end narrow and rounded. As the specimen 

 is an internal cast, it preserves no evidence of the surface characters. 

 The muscular scars are extremely faint and the pallial line undistinguish- 

 able, although the cast is in an excellent state of preservation and some- 

 what polished on the surface from the perfect condition. The hinge-line 

 has been marked by a large number of very fine teeth, gradually increasing 

 in size from the center outward. On the wider end of the shell there are 

 about twenty-five visible under a glass and about twenty somewhat stronger 

 ones on the narrower side of the beak. The ligamental pit has been of 

 moderate size, but well marked and deep." — Whitfield, 1885. 



Type Locality. — Hardeman County, Tennessee. 



Casts occurring in the Matawan, near the mouth of the Magothy Eiver, 

 have been referred to this species. They seem a little higher and less 

 smoothly rounded than Whitfield's gabbana, but agree very well in size 

 and general contour. Although the characters of the pallial sinus have 

 not been detected, the large size and the produced posterior end suggest 

 Yoldia rather than Leda. 



Occurrence.- — Matawan Formation. Ulmstead Point, Anne Arundel 

 County. 



