Ii2 CRUSTACEA——EU MALACOSTRACA CHAP. 
foliaceous limbs of the Phyllopods. The abdominal appendages 
are also biramous. The heart is greatly elongated, stretching 
through thorax and abdomen; there are present both the anten- 
nary excretory glands characteristic of adult Malacostraca and 
the maxillary glands characteristic of adult Entomostraca, and 
both the posterior and anterior livers characteristic of the two 
Orders respectively are present. This combination of characters 
justifies the belief that Nebalia represents a primitive form, 
standing to some extent in an intermediate position between 
Entomostraca and Malacostraca, but it may be doubted if the 
' special relationship to the Phyllopoda, claimed on the strength of 
the foliaceous appearance of the thoracic limbs, can be legitimately 
pressed. 
Nebalia shows the clearest signs of relationship to the other 
primitive Malacostraca, and especially to the Mysidae, which it 
resembles not only in general form and in the essentially 
biramous character of its appendages, but also in many embryo- 
logical points and in the similarity in development of the brood- 
pouch." 
A large number of very ancient palaeozoic fossils are known 
which are placed provisionally with Nebalia in the Division 
Phyllocarida, and some of these are no doubt closely related to 
the existing isolated genus. Hymenocaris from the Cambrian. 
SERIES 2. EUMALACOSTRACA. 
Before entering on a description of the members of this 
Series it is necessary to introduce and justify a new scheme of 
classification which has been proposed by Dr. W. T. Calman. 
This scheme necessitates the abandonment of the old Order 
Schizopoda, and also ignores the distinction which used to be 
considered fundamental between the sessile-eyed Crustacea 
(Edriophthalmata) and the stalk-eyed forms (Podophthalmata). 
The old group of Schizopoda, to which Nebalia and the isolated 
form Anaspides, to be considered later, are undoubtedly related, 
represent very clearly the stem-forms from which the various 
branches of the Malacostracan stock diverge. No doubt they 
are themselves specialised in many directions, since they are a 
dominant group in present day seas, but their organisation is 
! Robinson, Quart. J. Mier. Sci. 1., 1906, p. 383. 
