I \MKI.I. IKKANflllATA. ''"'' 



ban' 



the nut lino may !.. called Mil.circular, the bawil half, as a rule, lu'inn <piite regul 

 curved; length an<l hi^hl nearly equal, (lie latter dinien-inn commonly a little the 

 greater. Beaks prominent. -ituated behind the center, turned backwards. Surface 

 marked l>y comparatively strung concentric lines. 



On casts of the interior, and this is almost invariably the Condition in which the 

 species is preserved, the muscular scars are nearly always distinguishable and the 

 posterior one is often sharply defined and prominent on the upper side. They are 

 situated ju>t within the ends of the shell and each near the wider and lower end of 

 an obscurely defined >iilcns. The two sulci, of which the anterior one is usually the 

 better marked. l>gin near the beak and extend down on each side to the base of the 

 muscular scars. A small accessory scar has been observed immediately above the 

 posterior add ncti ii. I'allial line simple, rather distinct. Hinge plate comparatively 

 -triiii^. with numerous (at least thirty) small denticulations. 



The si/e of this shell varies greatly. Many of the specimens found at Cincinnati 

 and localities in the vicinity of that city are less than 2 mm. in diameter, but others 

 are occasionally met with that range from that size to a diameter of 5 mm. In the 

 northwestern localities the species grew to a larger size, specimens having a diameter 

 nf from 5 to 7 ram. being in the majority. Aside from the matter of size, however, 

 the specimens from these two regions are practically identical. 



I'r. S. A. Miller, in the work above referred to, erects a new genus, Palteoconrlm. 

 and a new family for the reception of the present species, which he divides into two 

 species, giving to the larger form the specific name faberi. But this new genus and 

 family have no right to recognition, since they are based entirely upon erroneous 

 observation, he having come to the conclusion that the hinge in these shells was 

 not denticulated and pml.al.ly edentulous. Through the kindness of Dr. Miller I 

 had an opportunity to examine a number of the specimens (excellent casts of the 

 interior) used by him in defining his genus. Even among these I noticed several 

 that retained undeniable evidence of the denticulate hinge. 



ation and locality. Very atuimlant al Cincinnati. < Mil... and numerotu other localities In the 

 ;>.. >. In i h- nortbwenl It is one of the rare fuMila of the so-called "Nuculm bed" 



of tin' Mu<|iikrta r llu<l>ri Kiv.-r shales. 



:N>NTA HAMBUROEHSI- I 

 I-I.ATI xi. ii KIGB. tad m. 

 Trllinomgat Hambrytn*U WAUtrrr, 1884. Pal. Kurckt I>ilrt< 



Shell small, r. >nvex, rounded-snlirhoml>oidal in outline, with the hijrht 



and length subequal and the beak coni| ly largo, incurved and -nu.it. -I in 



front of the center; posterior dorsal margin sotnewi tightened. Surface 



