648 ARTHROPODA SUB-KINGDOM VII 
Cambrian evolution was very rapid, and during the Ordovician they flourished as 
greatly as at any subsequent period. The prevailing Ordovician and Silurian types 
belong to the Leperditiidae and Beyrichiidae, although toward the close of the Silurian 
numerous Cypridae make their appearance. 
Devonian Ostracoda are less numerous, but manifest essentially the same types as 
in the earlier periods. Here, however, the larger Leperditiidae are entirely wanting. 
Although many small species of archaic genera persist in the Carboniferous, the aspect 
of the fauna is changed by the strong development of Cyprinidae. Thereafter but a 
meagre representation of Ostracods is met with until the Cretaceous, when certain 
genera, especially Cythere, develop a surprising variety and wealth of species. Little 
difference can be detected between Tertiary Ostracods and their modern descendants. 
[The above generic diagnoses of Ostracoda have been abridged from a more extended dis- 
cussion of the group, prepared for this work by Mr. E. O. Ulrich, of Newport, Kentucky.— 
TRANS. | 
Super-Order 4. CIRRIPEDIA. Barnacles. Latreille. 
Sessile, mostly hermaphroditic animals, enclosed in a membranous mantle which 
is often covered with calcareous plates. Body attached by the anterior extremity of the 
head ; obscurely, and at times not at all segmented ; posterior portion with at most 
six pairs of divided legs or cirri, which, however, may be fewer in number or altogether 
absent. 
The typical and best known Cirripedes (balanidae and Lepadidae) differ so 
widely from all other Crustacea in their external form, solid calcareous shells, 
slightly developed respiratory and sensory organs, and especially in their 
hermaphroditic sexual apparatus, that until 1830 they were commonly classed 
with the Mollusca. About this time J. V. Thompson and Burmeister showed 
1 Literature: A. Recent Forms. 
Thompson, J. V., Zoological Researches and Illustrations. I. Cork, 1830.—Discovery of the 
Metamorphosis in the Lepades, ete. (Phil. Trans. Roy. Soc., Pt. 2), 1835.—Burmeister, H., Beitriige 
zur Naturgeschichte der Rankenfiissler. Berlin, 1834.—Martin-Saint-Ange, G. J., Mémoire sur 
lorganisation des Cirripédes (Mém. Savans. Etrang. Acad. Sci. Paris, VI.), 1835.—Darwin, C., 
A Monograph of the Sub-Class Cirripedia (Ray Soce., I., I1.), 1851-54.—Hoek, P. P. C., Report on 
the Cirripedia (Rept. Challenger Exped., Zool., VIII., X.), 1883-84.—Aurivillius, C. W. S., Studien 
iiber Cirripeden (K. Svensk. Vetensk. Akad. Handl., XXVI., No. 7), 1893.—Groom, T. T., On the 
Early Development of the Cirripedia (Phil. Trans. Roy. Soc., 185), 1894.—Hansen, H. J., Phyllopoda 
and Cirripedia. Plankton Expedition, 1895. 
B. Fossil Forms. 
Sowerby, J., and J. de C., The Mineral Conchology of Great Britain. London, 1812-30.— 
Roemer, F. A., Die Versteinerungen des norddeutschen Kreidegebirges. Hanover, 1840-41.— 
Darwin, C., A Monograph of the Fossil Lepadidae of Great Britain (Palaeont. Soc.), 1851.—A 
Monograph of the Fossil Balanidae and Verrucidae of Great Britain (ibid.), 1854.—Bosquet, J., 
Monographie des Crustacés fossiles du terrain crétacé du Duché de Limbourg (Mém. Commiss. Carte 
geol. Néderlande), 1854.—Notice sur quelques Cirripédes recemment découverts dans les terrains 
erétacé du Duché de Limbourg. Haarlem, 1857.— Reuss, A. £., Ueber fossile Lepadiden 
(Sitzungsber. Akad. Wiss. Wien., XLIX.), 1864.— Woodward, H., On Turrilepas, etc. (Quar. Journ. 
Geol. Soe., XXI.), 1865.—Barrande, J., Systeme Silurien du centre de la Bohéme., I. Suppl. 1872.— 
Segquenza, G., Ricerche palaeontologiche intorno di Cirripedi terziarii della Provincia di Messina, 
Pts. L, Il. Naples, 1873-76. Marsson, J., Die Cirripeden und Ostracoden der weissen Schreib- 
kreide der Insel Riigen (Mittheil. naturw. Ver. Neu-Vorpommern und Riigen, XII.), 1880.—Zitte/, 
K. A., Bemerkungen iiber einige fossilen Lepaditen aus dem lithographischen Schiefer und der oberen 
Kreide (Sitzungsber. Bayer. Akad. Wiss., XIV.), 1884.—F aber, C. L., Remarks on some Fossils of the 
Cincinnati Group (Journ. Cincin. Soc. Nat. Sci., [X.), 1887.—Hall, J., and Clarke, J. M., Palaeon- 
tology of New York, VII. p. 209, 1888.—Clarke, J. M., Notes on certain Fossil Barnacles (Amer. 
Geol., XVII.), 1896.—Matthew, G. F., On occurrence of Cirripeds in the Cambrian (Trans. N. Y. 
Acad. Sci., XV.), 1896.—Logan, W. N., Cirripeds from Cretaceous of Kansas (Kansas Univ. Quar., 
VI.), 1897. 
