246 THE VOYAGE OF H.M.S. CHALLENGER. 
1. Actinal spines of the adambulacral armature very long, 
equal, delicate, needle-like, and slightly curved. 
Pedicellariz very small, resembling clavate papille. 
Infero-marginal plates with three spines, the lateral 
and median one long and equal, the inner one 
rather shorter. Rays long and gradually tapering. 
Paxillee with no robust central spinelet, but some- 
times two or three of the same size as the encircling 
series : : : : ; 5 ‘ : africana. 
2. Actinal spines of the adambulacral armature, short, 
cylindrical, equal, delicate. Pedicellarie very few, 
small, papilliform. Infero-marginal plates with 
three spines, the lateral and median one long and 
equal, the inner one smaller. Rays short and 
abruptly tapering. Paxille with a short robust 
central spinelet. . : : : ¢ . 
b, Adambulacral armature not forming a single transverse series continuous 
with the spines on the infero-marginal plates. 
a. Paxille at the sides of the rays with a slightly quadrate character. 
A large pedicellaria accompanies the outer spinelet on the 
actinal surface of the adambulacral plates ; the pedicellaria and 
spine standing as a pair side by side behind the single median 
and furrow spines 5 : : 3 ; : . : Forficifer. 
sarsi. 
Chorology of the Genus Luidia. 
a, Geographical distribution :-— 
AtLanTIc: Ten species between the parallels of 65° N. and 40° S. 
On the eastern side: Luwidia sarsi, in the northern area, from 
the coast of Norway to the British Islands. Lwidia ciliaris, from 
the Faerée Channel in the North to the Mediterranean. *Zuzdia 
africana, off the coast of Morocco and extending to the extreme 
southern point of Africa. Lwidia senegalensis, off the west coast of 
Africa, and extending to the Antilles and Brazil. 
On the western side: *Zwidia clathrata, extending from North 
Carolina, through the West Indian area, as far south as Brazil (Rio 
Janeiro).  Lwidea elegans, off North Carolina and in the West 
Indian area. Luidia variegata, in the Gulf of Mexico, off the mouth 
of the Mississippi. Luidia convexiuscula, Luidia barbadensis, and 
*Iuidia alternata, in the West Indian area, the last mentioned 
extending northward to the coast of Florida and southward to Bahia. 
Inpian Ocean: Three species between the parallels of 30° N. and 10° S. 
Luidia savignyi, in the Red Sea and off the east coast of Africa. 
LInidia maculata, in the Indian Ocean from the coast of Africa in 
