Bulletin of the Museum of Comparative Zoology II A R V A K D U N I \' K H S I 'V Y Vol. 131, No. !) KE VISED GENERIC DIAGNOSES OF THE FOSSIL FISHES MEGALICIITIIYS AND EOTOSTEOKHACHIS (FAMILY OSTEOLEPIDAE). By Keith Stewak'i' Thomson With One Plate CAMBRIDGE, MASS., U.S.A. PRINTED FOR THE MUSEUM July, 1964