PLATE XXXVIII. 



MODIOMORPHA MYTILOIDKS. 



Pafce i77. 

 Sc^ Plati' 37. 

 Figs. I-IH. A sfM'ies of speeiineiis illustrating' the principal varieties of form iiiiil sin-face characteiti of this 

 sjiecieH. In tig. 13 the valves ai-e still connected by the lig-ament. 

 Hamilton group. Eastern ami central Nno York. 



