SUPER-ORDER V MALACOSTRACA 653 
Order 1. PHYLLOCARIDA. Packard. (Leptostraca, Claus.) ! 
Body composed of five cephalic, eight thoracic, and two to eight abdominal segments. 
Head and thorax covered by a thin chitinous or partially calcified carapace, which 
may bein a single prece or divided into separate valves by a straight, unarticulated, 
single or double hinge. In front of the carapace is a narrow movable plate or rostrum. 
The head bears two pairs of antennae, and stalked compound eyes. Thoracic segments 
with soft phyllopodiform legs. Abdomen composed, of annular segments, and often 
ends in a spiniform caudal plate (telson) provided with lateral spines. 
The recent genus Nebalia (Fig. 1370) is regarded by Packard and Claus 
as the surviving representative of ancient Crustacean types, very numerous 
during the Palaeozoic, which had been previously classed with the Phyllopoda, 
but more properly form a distinct group (Phyllocarida) connecting the 
Entomostraca with the Malacostraca. The genus is very generalised, combining 
Copepod, Phyllopod, and Decapod-like features with other more fundamental 
characters of its own. Upon it is based largely the definition of the order, 
but some of the extinct families show structural differences from the living 
type which will eventually require their removal from this association. 
Cephalic appendages have not been satisfactorily determined in any fossil 
species, although traces of them have been noticed in a few genera (Cryptozoe, 
Ceratiocaris, Rhinocaris). In the absence of contrary evidence there is every 
reason to suppose that the appendages of the head, thorax, and abdomen were 
on the type of Nebalia, since there is such close correspondence in the form of 
carapace, rostrum, and abdomen. Owing to the non-preservation of limbs, 
distinctions within the group are based principally on vaitiations in the 
structure of the carapace, and in the number of body segments. Several 
fossil genera (Echinocaris, Rhinocaris, Mesothyra) bear a distinct optic node or 
pit, suggesting a sessile simple eye in contradistinction to the stalked faceted 
eye of Nebalia. In these genera, also, large cuspidate masticatory organs 
have been found, which were apparently attached only by means of muscles ; 
1 Literature: 
Salter, J. W., On some new Fossil Crustacea, etc. (Quar. Journ. Geol. Soc., XII. Dp: 265 exe ips 
75), 1856-62.—On New Silurian Crustacea (Ann. Mag. Nat. Hist., V. p. 153), 1860.—Hall, Jes 
Palaeontology of New York, II., 1859.—16th Ann. Rept. N.Y. State Cabinet Nat. Hist. 1863. 
—Woodward, H., On a new Genus of Phyllopodous Crustacea (Quar. Journ. Geol. Soc., XXII. 
p. 503), 1866.—Geol. Mag., IX. pp. 433, 563, 1872; IX. pp. 386, 444, 1882; II. pp. 345, 
385, 460, 1885.—Claus, C., Ueber den Bau und die systematische Stellung von Nebalia (Zeitschr. 
wissensch. Zool., XXII.), 1872.—Barrande, J., Systeme Silurien du centre de la Bohéme, I. 
Suppl. 1872.— Whitfield, R. P., Notice of new Forms of Fossil Crustacea, etc. (Amer. Journ. Sci. 
[3], XIX.), 1880.—Clarke, J. M., New Phyllopod Crustacea from the Devonian (Amer. Journ. Sci. 
[3], XXIII.), 1882.—New Discoveries in Devonian Crustacea (ibid. XXV.), 1883.—Ueber deutsche 
oberdevonische Crustaceen (Neues Jahrb., I. p. 178), 1884.—On the Structure of the Carapace in 
Rhinocaris, etc. (Amer. Nat., XXVII. p. 793), 1893.—14th Rept. State Geol. N.Y. L, 1898.— 
Packard, A. S., A Monograph of the Phyllopod Crustacea of North America (12th Ann. Rept. U.S. 
Geogr. Geol. Surv. Terr.), 1883.—Beecher, C. E., Ceratiocaridae from the Upper Devonian Measures 
(2nd Geol. Surv. Penn. Rept. PPP), 1884.—Jones, 7. R.,and Woodward, H., Various Papers in Geol. 
Mag., I.-X., 1884-94, and Reports 1-12 of Comm. on Fossil Phyllopoda Brit. Assoc. Adv. Sci., 1883- 
95.—Novdk, O., Remarques sur le genre Aristozoe (Sitzungsber. bohm. Akad. Wissensch. p- 239) 
1885.—(Jbid. p. 674), 1886.—On Occurrence of a New Form of Discinocaris in Bohemia (Geol. Mag. 
[3], IX. p. 148), 1892.—Sars, G. O., Report on the Phyllocarida (Leptostraca) Rept. Challenger 
Expedition, XIX., 1887.—Hall, J. and Clarke, J. M., Palaeontology of New York, VII., 1888.— 
Whitfield, R. P., New Genus of Phyllocaridae (Bull. Amer. Mus. Nat. Hist., VIII.), 1896.—Jones, 
T. R., and Woodward, H., Monograph of the British Palaeozoic Phyllopoda (Phyllocarida, Packard), 
Part III. (Palaeontogr. Soc.), 1898. _ 

