TH. MORTENSEN, 
(Schwed. Südpolar-Exp. 
The species represented in the collection of the South Polar Expedition are the 
following, those marked with an * being also represented in the collection of the 
Fuegian Expedition: 
Ctenocidaris speciosa n. g. n. sp. (South Georgia, Shag Rocks Bank, Graham Region). 
* Austrocidaris canaliculata (A. Ag.) (Falkland Isl.). 
— spinulosa n. sp. » » 
* Arbacia Dufresnii (Blv.) (Coast of North Argentina). 
* Notechinus magellanicus (Phil.) (Coast of North Argentina, Tierra del Fuego, Falk- 
land Isl., Graham Region). 
Sterechimts Neumayeri (Meissn.) (South Georgia, Graham Region). 
Agassizii nom. nov. (for » margaritaceus «) (Falkland Isl., South Georgia, 
Shag Rocks Bank, Burdwood Bank). 
* Loxechinus albus (MOL.) (Tierra del Fuego). 
Plexechinus Nordenskjöldi MRTSN (Shag Rocks Bank). 
* Abattis cavernosus (Phil.), with the variety bidens , n. var. (South Georgia). 
— Agassizii (PFEFFER) (South Georgia). 
* Schizaster ( Tripy laster) Philippii (Gray) (Coast of North Argentina). 
Amphipneustes Lorioli KOEHLER (Graham Region). 
— Koehleri Mrtsn (South Georgia, Shag Rocks Bank). 
The collection thus contains in all 14 species, 4 of which are new, viz. Cteno- 
cidaris speciosa , Austrocidaris spinulosa , Plexechinus Nordenskjöldi and Ainphi- 
pneustes Koehleri; of the two latter there has already been published a preliminary 
description. * The first of them also represents a new generic type. A new variety, 
bidens , had to be established for a form of Abattis cavernosus. The study of Arba- 
cia Dufresnii revealed the fact that a quite different species has hitherto been con- 
founded with it; this species is described here under the name of Arbacia crassispina 
n. sp. 
Among the more interesting points mentioned in the present work I may name 
the discovery, that Amphipneustes Koehleri shelters its brood, quite similar to 
what is known in Abattis cavernosus ; the description of the development of Abattis 
cavernosus , from the formation of the apical plates until it has reached maturity, 
the discovery of a distinct genital plate 5 being of special importance; further the 
discovery of the remarkable Phyto-Parasite, Echinophyces mirabilis , described from 
Rhynchocidaris triplopora Mrtsn in the »Echinoiden der deutschen Südpolar- 
Expedition», in Ctenocidaris speciosa , where it produces analogous effects, the genital 
openings being transferred to the middle of the corresponding interambulacra. 
Th. Mortensen. Some new species of Echinoidea. Vid. Medd. Naturh. Foren. Köbenhavn 1905. 
