INVERTEBRATE PAL2E0NTOLOGY. 253 



(called Machcera Moreana on d'Orbigny's plate), almost certainly belongs to 

 this group, unless there may be some differences in the character of its hinge, 

 which has not been described or illustrated. 



Lcptosolcii Conradi, Meek. 



Plate 2, figs. 12, a, h. 



Lcptosolen Conradi, Meek (1872), Hayden's Second Prelim. Ann. Report U. S. Geologic.il Survey of the 

 Territories, 1511. 



Shell elongate-oblong, nearly three times as long as high, moderately 

 convex; dorsal margin straight, pallial margin more or less nearly straight, 

 and subparallel to the dorsal, being a little convex in outline in front ot the 

 middle, thence ascending obliquely forward to the narrowly-rounded anterior 

 end ; posterior margin subf runcated verticalhy, but rounding abruptly into the 

 dorsal and ventral borders above and below ; beaks not raised above the 

 dorsal margin, and very inconspicuous, their position being only indicated 

 externally, by the curves of the marks of growth, located about one-third the 

 length of the valves from the anterior end; surface only showing fine lines 

 of growth. 



Length, 1.04 inches; height, 0.3G inch; convexity, 0.28 inch.. 



Internal casts of this species show the impression of the strong internal 

 ridge, extending directly downward from the beaks, and gradually dying out 

 below the middle of the valves.* These casts also show the impression of a 

 single small tooth in the right valve, just in front of the upper termination of 

 the deep furrow left by the strong internal ridge. From these characters, it 

 is evident that this genus is allied to Siliqua, Miihlfeldt (Leguminaria,Schum.), 

 but differs, as pointed out by Mr. Conrad, in having but a single hinge-tooth 

 in the right valve, instead of three in each valve. 



Compared with Mr/ Conrad's typical species, L. Uplicatus (Siliquaria 

 biplicata, Conrad, Jour. Acad. Nat. Sci., Ill, pi. 34, fig. 17), our shell is seen 

 not only to be much smaller and proportionally shorter, but to differ in not 

 having the two broad prominences radiating forward and downward from the 

 beak of each valve, as in that species, though it shows a single very obscure, 

 broad prominence, extending directly downward under the beaks, and widen- 

 ing as it descends. In front of, and behind this, there is also, in each valve, a 

 scarcely perceptible concavity. This broad prominence also imparts a slight 

 convexity to the outline of the base, just at the point where the base in Mr. 

 Conrad's species is sinuous. 



* It is a little too pointed below, and made to look too much like an accidental break, in our fignre. 



