IM.ATK XI. 



(il.YrroDESMA F.KRCTUM. 



Page IM. 

 See Plutes 12, 13, 25, 8t> and 87. 

 Fips. 1. 2. Two oppiisite valve.'i of the same iniliviiliuil. Vig. 2 sIkiws the nmsnilar scai- and alsn give.'! 

 the comparative elevation of the beak.s of the two valves. The left valve of the specimen 

 also shows the pallial line and niiiseidar impression, which ai'e not represented in the 

 ligure. 

 I'iir. ;>. A more entire left valve, haviiijf the eai-s but lilth'. extended. 

 I'iir. 4. A rig-ht valve having- the cardinal anjrles much produced. 



Hamilton {rrouj). Fidtoiiham, Schoharie Co.. N. Y. 

 Fiff. "i. A smaller right valve, showing one of the obliijue lateral teeth. 



Hamilton group. Cazeiiovia, JS. Y. 

 Kig. ti. A light valve, showing a iiroportionally gi-eater lireadtli. ami moderately extended cardinal 



ex|pansions. 

 Fig. 7. A portion of a large left valve with very large canliu.al alations. 



Hamilton gi'o\ij). MadiKnn Co., N. Y. 

 Fig. S. A left valve. Another figure of this .specimen is given on jilate 86. fig. IJ. 



Hamilton grouji. Cazmwria, N. Y. 

 Fig. 9. A large left valve with short broad i-ardinal angles and unusual height. The im)iression of the 



ligamental area is longitudinally striated. 

 Kig. 10. A left valve with the cardinal angles narrow and unusually extended. This form is the Avh-nla 

 cruciformis, Co.NRAn. Ann. Rep. ]?. .")4. 1S41. The specimen preserves the pallial line and 

 nuisrular inipressiim, which are not shown in tlii' figure. 



