I.AMKI.I.llii: \N IIIATA. '..'7 



Kado4B orU>M>ti 



OODK8MA P<> 



I'l.ATK XXXVII. KlOS.t lad*. 



Of this species I have seen only a single imperfect -pf-mien which under 

 ordinary circum-tance-* \\oiild scarcely merit description. Being however the most 

 recent existence of the genus now known it i- of interest as it may give us a clue to 

 tin- later development of the genus. As may be seen from the figures the species is 

 closely related to / '// but, as the name implies, the posterior width (bight) 



is greater in /.. fH>st/ntiii. In a cardinal view both ends also are more obtuse, giving 



ter convexity to the sides; the umbonal ridge, though prominent, is not so 

 -harply rounded. the umbones fuller, the anterior end shorter, and the posterior 

 margin more !>r<>a<lly rounded and most prominent in the basal half instead of near 

 the middle. Finally, the mesial sulcus crosses the valves more obliquely and the 

 simiation of the ventral margin is wider and nearer the center of the length of the 

 shell. 



The side view of this shell is considerably like that of several species of Modio- 

 Injixis. tuit the absence of a strong anterior muscular scar on casts and the presence 

 of the concave areas bordering the hinge line proves that it is not a Mwliolopsis but 

 an Kndodtsma. 



Formation and locality. Uppermost bcdH of the Galena, I>ul>u<|ti. Iowa, where It was collected by 

 Mr. Charle* Srhuchrrt. 



Mut. Reg. No. 8345. 



DODR8MA ORTHONOTUM Meek and \\'urllien. 



PI./VTK \\.\VII. FIGS. I ami* 



Modioloptu orthonota MBKK and WOKTIIKN. I-<6<, Cny.l Sur. III., vol. Ill, p. 206. 

 ModioloptU reetiformu WUKTIIKN. ISO; Hull. N... 1, II! .. 



Shell elongate, the length being nearly three tinn-i the hight; valves quite 

 convex, the greatest convexity being a short distance above the middle, in front of 

 which they have an undefined concavity commencing in the umbonal region and 

 widening and deepening to the base in front of the'middle. Cardinal margin long, 

 very nearly ->traight or but slightly arrhcd; posterior margin oMiquely substrunca- 

 ted, sometimes very faintly sinuous above, and rather narrowly rounded below the 

 middle; basal margin <ubparallel to the dorsal, gently convex behind the middle. 

 and broadly sinuous between the middle and the front; anterior side short, con - 

 t r.i.-ted beneath the beaks, narrowly rounded. Beaks depressed, appearing on a line 

 with the dorsal margin, -trongly incurved, placed abont one-sixth of the entire 

 length of the valves behind the anterior extremity; lunule rather large but not 



