THE PHYLLOCARIDA. 5 



Baird (1850) founded the family Nebaliada, and regarded Nebalia as a Phyllopod. 



Prof. J. D. Dana (1853), in his great work on the Crustacea, retained the family 

 name (Nebaliada), and he placed the family in the Phyllopoda. 



Metschnikoff in 1865 published an abstract of his account of the development 

 of Nebalia Geoffroyi, and in 1868 the full essay in the Russian language. Fritz 

 Miiller, in his * Fiir Darwin,' states that Metschnikoff has observed " that Nebalia, 

 during its embryonal life, passes through the ' Nauplius and Zoea stages,' which 

 in the Decapoda occur partly (in Penaus) in the free state." " Therefore," he 

 adds, " I regard Nebalia as a Phyllopodiform Decapod." 



In 1872 Claus gave an account, with excellent figures, of the external anatomy 

 of Nebalia Geoffroyi, and in 1876 he described the internal anatomy. 



In 1875 in the account of the Atlantic Crustacea of the " Challenger Expedition," 

 Willemoes-Suhm placed the Nebaliada among the Schizopoda. 



In 1879 Dr. A. S. Packard, jun., in the ' American Naturalist,' vol. xiii., p. 128, 

 proposed that Nebalia and its fossil allies should be placed in a new order, which 

 he proposed to name the Phyllooaeida. Dr. Packard writes : 



" The Nebaliada, represented by the existing genus Nebalia, have generally 

 been considered to form a family of Phyllopod Crustacea. Metschnikoff, who 

 studied the embryology of Nebalia, considered it to be a ' Phyllopodiform Decapod.' 

 Beside the resemblance to the Decapods, there is also a combination of Copepod 

 and Phyllopod characteristics. The type is an instance of a generalised one, and 

 is of high antiquity, having been ushered in during the earliest Silurian Period, 

 when there were (when we regard the relative size of most Crustacea, and especially 

 of living Nebalia) gigantic forms. Such was Dithyrocaris, which must have been 

 over a foot long, the carapace being seven inches long. The modern Nebalia is 

 small, about half an inch in length, with the body compressed, the carapace bivalved 

 as in Limnadia, one of the genuine Phyllopods. There is a large rostrum over- 

 hanging the head ; stalked eyes ; and, besides two pairs of antennas and mouth- 

 parts, eight pairs of leaf-like, short, respiratory feet, which are succeeded by 

 swimming-feet. There is no metamorphosis, development being direct. 



" Of the fossil forms, Hymenocaris was regarded by Salter as ' the more 

 generalised type.' The genera Peltocaris and Discinocaris characterise the Lower 

 Silurian Period, Oeratiocaris the Upper, Dictyocaris 1 the Upper Silurian and the 

 lowest Devonian strata, Dithyrocaris and Argas 2 the Carboniferous Period. Our 

 existing north-eastern species is Nebalia bipes (Fabricius), which occurs from Maine 

 to Greenland. 



" The Nebaliads were the forerunners of the Decapoda, and form, we believe, 

 the type of a distinct order of Crustacea, for which the name Phyllooaeida is pro- 



1 Of doubtful alliance. 2 Not separate from Dithyrocaris. 



