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We see in the echinoderms to-day most perplexing combinations of primitive and highly speciahzed characters associated in all sorts of ways, and this leads naturally to the assumption that there was no definite intergradmg form between the echinoderms and the barnacles, which, of all the Crustacea, approach them most closely, but that the former sprang from the phylogenetic fine, wliich maj-by easy stages be traced to the latter, by a broad saltation in which the assumption of the free habit (subsequently modified in the Pelmatozoa) and the correlated assumption of pcntamerous symmetry combined to make the existence of intei"grading forms impossible, while at the same time it resulted in the formation at the very moment The coniatulids must therefore be considered as a biologically extremely complex and mixed group in which each organ and structure occurs in a single series all the way from a jirimitive to a highly specialized type, but in which the various degi-ees of specialization of each organ or structure, in other words, the progressive steps in the series, as not in any way correlated with species or with genera, or with the comparable degrees of specialization of any other organ or structure.Thus it is at once evident that there is a most extraordinary uniformity tliroughout all the comatulid families and genera, and that each is potentially on essentially the same phylogenetic plane as are all of the others.The comatulids as a group are exactly parallel and comparable to the pentacrinites as a group; they are descended from the same ancestral stock and represent exactly the same phylogenetic stage, but durmg their development they have diverged from their )>hylogenetic mean m exactly the opposite direction. The pentacrinites have departed \vidcly from their ])rotot_v]5es by enormously increasing the length of the column and at the same time indefinitely reduplicating the cirriferous proximale, a dei>arture which has to a considerable degree lessened the mobility of the crown, this bemg in part compensated by a corresp(mdhig mcrease m the length of the arms; while the comatulids have departed just as widely by compressmg what is virtually the entire column of the pentacrinites within the comi)ass of the single ])roximale or nodal from which numerous cirri are extruded, fixation by these cirri reducing the possibility of motion bj^the crown to a minimum so that under ordinary conditions the animals are almost as firndy attached as is IIolopus.As the greater part of the enormously elongated stem of the pentacrinites lies on the sea floor and therefore becomes neutral in its relation to the mechanics of the animals, these forms do not exhibit any very radical departure from a more generalized tjqie, such difl'erences as they show being chiefly the result of the very large size of the cro\ni and arms correlated with a reduction in size of the calyx ; nor do The pentacrinites thus continue to build a long, many-jointed stem, while the comatulids condense the entire stem withm the compass of the fu-st-formed n...

In revising the genera and species of the large comatulid family Antedonidae, it was found that a more precise definition of certain generic groups was desirable. This is made possible by the creation of three additional genera the recognition of which will assist in bringing out more clearly the true interrelationships of the species in the groups concerned. In addition to these three genera there are described herein a new genus based upon a hitherto undescribed species from the northeastern Pacific and a genus that has long been used by the author but never formally diagnosed. A small West Indian comatulid recorded from the Blake collection by Dr. P. H. Carpenter as Antedon hagenii was for a long time a mystery, as none of the specimens were received by Hartlaub when, after Carpenter's death, the Blake collection was sent to him. This now turns out to be a species quite dift'erent from Coccometra hagenii, and it is described below as Compsometra nuttingi. It is assigned to the genus Compsometra with some misgivings, but until more adequate and more extensive material is available it seems better to place it here than to create a new genus for it.

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