54 



CLASSIFICATION OF THE ANIMAL KINGDOM. 



The genus Nebalia is a transitional form, which is in many respects 

 intermediate between the Phyllopods and the Stomapods. By its de- 

 velopment it would appear to be referable rather to the Malacostra'ca 

 than to the Entomostraca, in which case it must be placed in or near the 

 order of the Stomapoda. 



(Glaus, Beitrage zur Kenntniss der Entomostraken, Marburg, 1860 ; 

 Grube, Ueber die Gattungen Estheria und Limnadia und einen neuen Apus, 

 Archiv fiir Naturg., 1865.) 



ORDEK V. *Trilobita. Asaphus, Calymene, Illcenus (fig. 49), 

 Agnostus, Paradoxides. 



(Barrande, Systems Silurien de la BoMme, vol. i., 1852 and 1872.) 



Fig. 49. A, A complete example of Ilbenus Davisii, in its unrolled state. B, Hypostomeof 

 the same, c, Illcenus (Bumastus) Barriensis, rolled up. Lower Silurian. (After Salter.) 



ORDER VI. MEROSTOMATA. 



Sub-ord. 1. Xiphosura. Limulus. 



Sub-ord. 2. *Eurypterida. Pterygotus, Slimonia. 



(Owen, On the Anatomy and Development of the American King Crab, 

 Trans. Linn. Soc., 1872 ; Packard, The Anatomy, Histology, and Embry- 

 ology of Limulus polyphemus, Anniversary Mem. of the Boston Soc. Nat. 

 Hist., 1880 ; Kay Lankester, Limulus an Arachnid, Quart. Journ. Micros. 

 Science, 1881 ; H. Woodward, Monograph of the Fossil Merostomata, Pala> 

 ontographical Society, 1866-72.) 



Various authorities at the present day are of opinion that Limulus 



