445 
layer at the external membrane of the ovisacs being quite dissolved, 
constituting a uniformly granular substance. 
Locality. It has already been mentioned that the animals 
have been found in secondary spines of the Echinothurid Calveria 
gracilis (Ag.); the specimen in question has been secured by the 
»Challenger" Stat. 200: (Lat. 6247' N. Long. 1249 28' E.; 250 
fathoms), Philippine Islands. 
III. Position in the System. 
In 1899 Dr. W. Giesbrecht published his voluminous and 
very valuable monograph: Asterocheriden (Fauna und Flora des 
Golfes von Neapel. ..….. 25. Monographie). From the beginning 
of the investigation of my new form I supposed that it probably 
belonged to the family named, and I have taken care to examine 
nearly all the external features mentioned by Giesbrecht in his 
fine work. My description of the female agrees moderately well with 
the diagnosis of the family Asterocheridæ given by Giesbrecht on 
p. 96. The antennæ, the sipho, the maxillæ, the maxillipeds, the 
four pairs of natatory legs and the fifth thoracic segment with its 
rudimentary legs agree completely; the antennulæ differ only by 
possessing a number of thick setæ with the apex a little swollen 
and emarginate; the maxillulæ differ scarcely in points of importance. 
The skin on the sides and on the dorsal surface of the enormous 
head is evidently weaker and more membranous than in the animals 
studied by Giesbrecht, but this feature, which coincides with the 
habitation of our parasite, is of slight systematic importance. I can 
point out only two more important differences between the new form 
and the Asterocheridæ of Giesbrecht. The number of the. really 
abdominal segments is still more reduced, only two being present, 
while three or four are met with in earlier known forms; on the 
" ventral side the head is separated from the first thoracic segment 
by a narrow membrane, while the head and the first thoracic seg- 
ment are coalesced in the other genera. But the differences dis- 
