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“ 
ON THE FOSSIL PHYLLOPODA OF THE PALAOZOIC ROCKS. 331 
partly (in Penews) in the free state.’ ‘ Therefore,’ he adds, ‘I regard 
Nebulia 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 ‘Chal- 
lenger’ Expedition, Willemoes-Suhm placed the Nebaliade among the 
_ Schizopoda. 
In 1879 Dr. A. 8. Packard, jun., in the ‘ American Naturalist,’ 
yol. xiii. p. 128, proposed that Nebalia and its fossil allies should be 
placed in a new order, which he proposed to name the PHYLLOCARIDA. 
Dr. Packard writes :— 
‘The Nebaliade, 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.”” Besides 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, 
haying been ushered in during the earliest Silurian period, when there: 
were (when we regard the relative size of most Crustacea, and especially 
of living Nebalic) gigantic forms. Such was Dithyrocaris, which must: 
have been over a foot long, the carapace being seven inches iong. The 
modern Nebalia is small, about half an inch in length, with the body com- 
pressed, the carapace bivalved as in Limnadia, one of the genuine Phyllo- 
pods. There is a large rostrum overhanging the head; stalked eyes; 
and, besides two pairs of antenne 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 charac- 
terise the Lower-Silurian period, Ceratiocaris the Upper, Dictyocaris the 
Upper-Silurian and the lowest Devonian strata, Dithyrocaris and Argas 
i Carboniferous period. Our existing north-eastern species is Nebalia 
bipes (Fabricius), which occurs from Maine to Greenland. 
_ ‘*The Nebaliads were the forerunners of the Decapopa, and form, we 
believe, the type of a distinct order of Crustacea, for which the name 
Puyxiocaripa is proposed.’ 
The order Payiuocaripa has been thus defined :— 
Puytiocartwa, Packard (1879). Body long, with five cephalic, eight. 
thoracic, and eight abdominal segments, with a thin or chitinous skin, 
Nae covered with a bivalved shell having a movable rostrum. 
ler 
es pedunculated and faceted. Upon the under side of the head are 
two pairs of antenne ; the mandibles and two pairs of maxille furnished 
with palpi. The body-segments are compressed, they support eight pairs 
of large Phyllopodiform thoracic feet. The abdomen composed of eight 
rge segments,' provided with six pairs of simple swimming-feet fringed 
with setge, of which the four anterior pairs are the largest, and the two 
posterior pairs are very small. The abdomen terminates in setaceous 
laments, or in a telson divided into three or more parts. (Zittel, 
“Handbuch der Paliontologie,’ Munich, 1885.) 
__ } The abdomen is nine-jointed, unless the last somite be considered as the telson 
(it is post-anal). It is a long and slender segment, and bears two very long narrow 
Setigerous cercopods, closely resembling those of the Copepoda. 
