and on Nehalia, and its Allies. 351 



2. The moveable rostrum, loosely attached to the carapace. 



3. The very long and large mandibular palpus ; the long slender 

 ap^Dendage of the first maxilla, and the very long bi-ramous maxillae. 



4. • The absence of any maxillipeds. 



5. The eight pairs of pseudo-phyllopod tlioracic feet, not adapted 

 for walking. 



[To these we would add : — 5a. The ' telson ' long and slender, 

 with two long narrow setigerous cercopods as in the Copepoda.] 



6. The animal swimming on its back. 



7. No zoea-formed larva. 



The characters which separate it from the Phyllopods are : — 



1. Carapace not hinged ; a rostrum present. 



2. Two pairs of well-developed long and large multiarticulate 

 antenuEe ; the hinder pair, in the male, longer than the first pair. 



3. The thorax and its appendages clearly differentiated from the 

 abdomen." ^ 



Nebalia has been so long regarded as the surviving representative 

 of those more ancient and gigantic forms of Phyllocarida, which 

 existed in such, numbers in the Cambrian and Silurian Seas, and 

 became nearly extinct towards the close of the Carboniferous epoch, 

 that any decision affecting its zoological position cannot be a matter 

 of indifference to the palgeontologist. 



But after studying its larval development, and adult structural 

 modifications, we arrive at the fact that Nebalia is a more generalized 

 type than is ordinarily to be found at the present day, " combining 

 Copepod, Phyllopod, and Decapod-like features, with other more 

 fundamental characters of its own," * which preclude us from re- 

 garding it as a true Malacostracan, and, although ancestrally related 

 to that order, it nevertheless does not attain in my opinion to the 

 Malacostracan grade of development.^ They should therefore be 

 arranged in a distinct order (the Phyllocarida), between the Ento- 

 MOSTRACA and the Malacostraca, as suggested by Claus. But if it 

 is undesirable to have such an outstanding group, then I contend 

 that the balance turns in favour of retaining it in the former division, 

 if not indeed in the order Phyllopoda as heretofore. 



"It is," writes Prof. Claus, "in the highest degree probable, how- 

 ever, that all these " (Palaeozoic PnYLLocARiD^a;) " are not true Phyllo- 

 pods, but have belonged to a type of Crustacea, of which now there 

 are no living representatives, but which, taking their origin from 

 forms allied to the lower types of Entomostraca, have prepared the 

 way for the Malacostracan type. Such a connecting link, which has 

 served to the present day, we evidently find in the genus Nebalia." * 



^ American Naturalist, 1882, vol. xvi. p. 951 ; and Monograph N. Amer. 

 Phyllopods, etc, 1883, pp. 447-8. 2 Packard. 



^ Dr. Packard writes, " There is little to indicate that the Schizopods {Mi/sis, etc.) 

 have descended from a Nebalia-\ike form, but rather from some accelerated zoca 

 form ; while the Phyllocarida have had no Decapod-blood in them, so to say, but 

 have descended by a separate line from Copepod-like ancestors, and culminated, and 

 even began to disappear, before any Malacostraca, at least in any numbers, appeared " 

 (American Naturalist, 1882, vol. xvi. p. 873). 



1 Claus in Siebold and Kolliker's Zeitschrift, xxii. 1872, p. 329. 



