742 
THE VOYAGE OF H.M.S. CHALLENGER. 
several species from the Nauplius stage through all the many successive stages up to 
the adult form. 
“ The fourth subdivision of the Schizopoda, the Mysidee, is represented both by deep- 
sea forms and pelagic species. Of the first group a very peculiar form, Petalophthalmus 
armiger, has been described by v. Willemoes Suhm, distinguished by the rudimentary 
leaf-like eyes and more particularly by the very remarkable appearance of the male, in 
which the antennules, mandibular palps, maxillipedes, and partly also the legs, are very 
peculiarly modified. Another very large and handsome form from the Subantarctic Sea 
has been referred by v. Willemoes Suhm to the same genus, but is evidently not 
congeneric with Petalophthalmus armiger , although it exhibits a similar reduction of the 
visual organs. It has proved to be identical with a form described by Professor Sars 
as Boreomysis scyphops from the depths of the Arctic Sea, thus exhibiting another 
instance of a very peculiar geographical distribution, the very same species being found 
in the corresponding region in both hemispheres, without occurring in the wide inter- 
mediate space, comprising both the temperate and the tropical zones. Two more 
Mysidians with imperfectly developed lamelliform eyes have been collected in the 
southern hemisphere, both of which belong to the boreal genera Amblyops and 
Pseudomma, G. 0. Sars, differing only very slightly from Norwegian species. 
“ Of pelagic Mysidae, five species are represented in the collection. One of these, which 
has been collected off the Cape of Good Hope, belongs to the genus Auchialus of Kroyer, 
and is apparently identical with the typical species described by that author. Of the 
genus Siriella, Dana (or Cynthia, Thompson), the two species Siriella thompsonii, Edwards, 
and Siriella gracilis, Dana, seem to have a very wide geographical distribution, being 
found in nearly all parts of the oceans traversed by the Expedition. The two remain- 
ing pelagic species of Mysidae belong to a new genus, Euchcetomera, chiefly distinguished 
by the strongly plumose setae on the several limbs, as also by the peculiar form of the 
telson. Both species were caught in the Pacific.” 
The Cumacea. — “ The Cumacea are rather scantily represented in the collection, only 
eleven species having been secured, which may perhaps be accounted for by their 
generally small size and inconspicuous colours, causing them easily to be overlooked in 
the rough examination of the dredged material. Most of the species belong to the genus 
Diastylis, some of which were taken in very considerable depths, viz., down to 2025 
fathoms. Perhaps the most striking among the Challenger Cumacea is a very slender 
form from the coast of Kerguelen Island, Hemilamprops serrato-costata, G. 0. Sars, of 
which numerous specimens were collected during the stay of the Expedition at Christmas 
Harbour. In examining a parcel of dredged mud from this locality (120 fathoms), 
several more specimens have been picked out, showing ' that this form occurs there in 
great profusion. The examination of the mud also yielded a great quantity of other 
