to them, has been expounded by Professor Giard, namely, that it tends to obliterate the secondary sexual characters. Modern research has discovered no crab to surpass _Macrocheira kämpferi_, De Haan, that can span between three and four yards with the tips of its toes, but at the other end of the scale it has yielded _Collodes malabaricus_, Alcock, "of which the carapace, in an adult and egg-laden female, is less than one-sixth of an inch in its greatest diameter." The most abyssal of all crabs yet known is _Ethusina abyssicola_, Smith, or what is perhaps only a variety of it, _E. challengeri_, Miers. Of the latter the "Albatross" obtained a specimen from a depth of 2232 fathoms (Faxon, 1895), of the former from 2221 fathoms, and of this S. I. Smith remarks that it has "distinctly faceted black eyes," although in them "there are only a very few visual elements at the tips of the immobile eye-stalks." The _Brachyura anomala_, or Dromiidea, "have preserved the external characters and probably also the organization of the Brachyura of the Secondary epoch" (Milne-Edwards and Bouvier, 1901). They agree with the true crabs in not having appendages (uropods) to the sixth segment of the pleon, the atrophy being complete in the Homolidae and Homolodromiidae, whereas in the Dromiidae and Dynomenidae a pair of small plates appear to be vestiges of these organs. In the family Homolidae stands the strange genus _Latreillia_, Roux, with long slender limbs and triangular carapace after the fashion of oxyrhynch spider-crabs. In _Homola_ the carapace is quadrilateral. Between these two a very interesting link was discovered by the "Challenger" in the species _Latreillopsis bispinosa_. Henderson. Bouvier (1896) has shown that _Palaeinachus longipes_, Woodward, from the Forest Marble of Wiltshire, is in close relationship, not to the oxyrhynch Inachidae, but to the genera _Homolodromia_ and _Dicranodromia_ of the Homolodromiidae, and that the Jurassic crabs in general, of the family Prosoponidae (Meyer), are Dromiidea.