Since any work in this group must of necessity be a review of that done by the late Dr. Geo. D. Hulst, I want to state in this begining of mine, that it is not to be regarded as a criticism.

Dr. Hulst made (for him) some curious errors, which will be noted later on, but the immense work he did in untangling the synonymy of this variable group, and in his two trips across the ocean to study the types, cannot be overestimated, and by it mine is rendered easy.