Halamphora is a genus that used to be considered a sub-genus of its close relative Amphora, but has now been made into its own genus.  Halamphora differs from Amphora in a number of subtle ways: most noticeably its marginal ridge, the distinct cutoff between the face and side of the diatom, is not well defined and instead gradually slopes to become the side of the diatom.   This can be seen in the picture below, in contrast to the photo of an Amphora used in the diagram to the right.  Additionally, many species of Halamphora do not have a fascia (blank area) present on the dorsal side, while many Amphora do.  Finally, the two genera are separated by environment: most Halamphora live in saltwater and marine environments, although some do still live in freshwater.