Maryland Geological Survey 503 



The genus is known to recede well back into the Mesozoic. As in a 

 number of other ancient types, the reduced survivors have been able to 

 maintain their existence only in those areas unfavorable to molluscan life 

 where the competition is relatively slight. 



The recent Amauropsis are typically boreal in distribution. 



A. Maximum diameter is equal to two-thirds of the total altitude, maxi- 



mum diameter of the body whorl near the median horizontal of the 

 whorl Amauropsis meekana 



B. Maximum diameter less than two-thirds of the total altitude, maxi- 



mum diameter of the body whorl in front of the median horizontal. 



Amauropsis compacta 



Amauropsis meekana Whitfield 



Amauropsis paludinaformis Gabb, 1876, Proc. Acad. Nat. Sci., Phila., p. 296. 



(Not A. paludinaformis Hall and Meek, 1855.) 

 Amauropsis meekana Whitfield, 1892, Mon. U. S. Geol. Survey, vol. xviii, 



p. 131, pi. xvi, figs. 22-25. 

 Amauropsis meekana Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 21. 

 Amauropsis meekana "Weller, 1907, Geol. Survey of New Jersey, Pal., vol. 



iv, p. 681, pi. lxxvii, figs. 1-3. 



Description. — " Shell of medium size, elongate-subovate ; spire moder- 

 ately elevated, only about two-thirds as high above the aperture as the 

 length of the aperture ; volutions five or five and a half in the largest speci- 

 men ; ventricose, with distinct, well marked sutures, which are very slightly 

 channelled ; body volution more distinctly ventricose than the others ; axis 

 solid ; aperture ovate, acute at the upper end, rounded and slightly effuse 

 below ; outer lip thin and sharp ; columella somewhat thickened by the 

 deposit of the lip, and grooved below the margin of the deposit, but not 

 umbilicate ; surface of the shell marked by proportionately strong, trans- 

 verse lines of growth, which are exceedingly irregular ; and also by fine, 

 even, corrugated spiral lines crossing them." — Whitfield, 1892. 



Only a single imperfect cast apparently referable to this species was col- 

 lected from the Matawan. It is a much larger shall than ,4. compacta, 

 and relatively slender. 



Occurrence. — Matawan Formation. Post 105, Chesapeake and Dela- 

 ware Canal. Delaware. 



Collection. — Maryland Geological Survey.' 



