EASTMAN: STRUCTURE AND RELATIONS OF MYLOSTOMA. 29 



nately not preserved for its entire length, but would seem to have been 

 at least 15.5 cm. long, exclusive of its terminal process. The dimensions 

 of the ventro-lateral plates cannot be determined with any great nicety, 

 but although exhibiting about the same proportions, they are fully one- 

 fifth smaller than the corresponding elements in the unique example of 

 Mylostoma figured by Dean. 



