Of all the Paleozoic Stelleroidea (174 species), not a single one is common to North America and Europe. Of genera having specific representation in more than one continent, a short list is presented. Nearly all of the species have very short geologic ranges, but very few occuring in more than one single formation. This memoir had its inception in 1896 when the writer was made aware of the desire of Mr. I. H. Harris, of Waynesville, Ohio, to present to the institution his extensive collection of Ordovician fossils, which brought to the National Museum 40 Asterids, 35 ophiurids from the Cincinnatic strata and 12 specimens of Onychaster flexilis. The material of the Harris collection study revealed much new knowledge, as well as shedding information on the probable evolution of the Paleozoic starfishes.