483 



OSTRACODA. 



IN the order called Ostracoda a term derived from a Greek word, signifying a shell 

 the cuirass is in two parts, and incloses the animal like a bivalve shell. The hind jaws are 

 furnished with gills. In the family of the Cypridae, the upper pair of antennae are long, have 

 numerous joints and a pencil of long filaments ; the lower pair are short, thick, and used as 

 feet. There are two pairs of real feet. One of these creatures is called CYPEIS. It belongs 

 to a genus which has many European species, and it may be found in almost every pond or 

 ditch. The body is inclosed thoroughly in its valved cuirass, something like a walnut in its 

 shell, the fringed antenme and legs protruding from between the valves and permitting the 

 creature to move. It is a most elegant little being, the shell being gracefully curved, and the 

 antennas being fine and transparent as if they were threads of glass. Dr. Baird tells us that 

 the valves are very brittle, and that on their exterior they are washed with a kind of var- 

 nish which protects them from the action of the water. Owing to this varnish, these 

 creatures cannot venture even to rise to the surface ; for as soon as the shell is exposed 

 to the air, it becomes quite dry, and so buoyant, that no exertion of the Cypris can sink 

 it again. 



These tiny animals will often live through a hot summer which dries up the pond in which 

 they reside, and at the first rain will make their appearance again, swimming merrily about as 

 if nothing had happened. As soon as they feel themselves being deserted by the water, they 

 bury themselves deeply in the mud, and even their eggs retain their vitality, though the mud 

 should be baked quite hard. When the Cypris changes its skin, it throws off the whole shell, 

 the internal parts of the body, the beautiful comb-like gills, and the tiny hairs which clothe 

 the bristles of the antenna?. 



Two other examples of this pretty genus are named Cypris clavdta and Cypris vidua. 



IN the family of Cytheridre, the upper pair of antenna? have no long filaments. 



The members of the typical genus Cythere are mostly marine, and may be found in the 

 little rock-pools at the sea-side, darting about among the branches of sea- weeds and zoophytes 

 that live so plentifully in such situations. Safe in these sheltered spots, they care nothing for 

 wind and waves, and the storm which flings the huge whale on the shore will fail to injure 

 these tiny beings, whose very minuteness is their safety. One species, Cythere minna, is 

 remarkable for being the largest one seen by Dr. Baird. Its valves are white. It was found 

 in deep water and taken in a dredge. Cythere inopinata derives its specific name of inopinata 

 or unexpected, from the fact that the creature was found where no one would have expected 

 its presence, namely, in small ponds. It is a very small species, and always remains at the 

 bottom. Its color is white, and there is a little orange-colored mark on the upper edge. An 

 oblique view of this species has been chosen, in order to show the curious rounded projections 

 upon the middle of each valve. 



The Cythere impressa was found in sand at Torquay. The shell is dull black in color, 

 and is covered with little punctures impressed upon its surface, whence is derived its specific 

 name. 



A closely allied genus is remarkable for the manner in which the valves are ridged, 

 irregular, covered with tubercles, and having their edges boldly toothed. This species was 

 taken in the Isle of Skye. 



IN the family of the Cypridinadsfi there are two eyes, set as footstalks, and two pairs of 

 feet, one pair being always within the shell. There is only one genus of these creatures, and 

 all the species are marine. The shell is oval, sharply pointed at each end, and the front edge 

 is deeply notched. The pair of feet that are retained within the shell are modified into one 

 organ, which seems to be intended for the purpose of supporting the eggs. Some other 

 species are luminous. 



