THE OSTRACODA 



SUB-CLASS OSTRACODA, Latreille (1802). 



Order 1. Myodocopa. 



2. Cladocopa. 



3. Podocopa. 



4. Platycopa. 



Definition. Crustacea in which the carapace forms a bivalve 

 shell ; the trunk is indistinctly segmented, its posterior part is 

 without limbs and ends in a caudal furca; the antennules and 

 antennae are large and used for locomotion ; the mandibles have a 

 palp ; not more than four pairs of limbs are distinctly developed 

 behind the mandibles and they vary much in form ; the genital 

 apertures are behind the last pair of limbs ; the paired eyes are 

 sometimes present ; development with metamorphosis, the young 

 hatched in the form of a modified nauplius. 



Historical. Although various species of Ostracoda were seen 

 and figured by the early microscopists, the scientific study of the 

 group may be said to begin with 0. F. Miiller's Entomostraca 

 (1785). The bivalve shell caused these animals to be associated 

 in most of the earlier systems of classification with the Cladocera, 

 from which they were separated by Milne-Edwards (1840). Almost 

 the first to give an account of the internal anatomy was Zenker. 

 The knowledge of their development is based chiefly on the works 

 of Glaus. The systematic and faunistic works of G. 0. Sars, Brady, 

 and Norman are among the most important ; while in recent years 

 G. W. Muller has made noteworthy advances towards a precise and 

 detailed knowledge of morphology and classification. 



MORPHOLOGY. 



The bivalved shell which completely encloses the body and limbs 

 (Fig. 33) is usually elliptical in outline as seen from the side, often 

 (Podocopa) somewhat flattened ventrally, but it may be nearly 



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