8 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
cannot but wonder how these creatures can live, and thrive, in the dis- 
gustingly impure water of Havana harbor. It is, however, well known 
that the Discophoræ in general seem to prefer the relatively impure 
waters of bays to that of the open ocean. Dactylometra lactea is much 
smaller than its northern ally, D. quinquecirra. Fully developed speci- 
mens measure only 65 mm. across the disk, while the young individual 
figured upon Plate IX. was only 40 mm. in diameter. 
