1889.] ON SOME PRE SH WATER OSTRACODA AND COPEPODA. 17 



of 2 superposed plates, the inner exhibiting a rounded triangular 

 form, whereas the outer projects beyond the latter as a narrow, 

 slightly incurved, linguiform lobe, obtuse at the extremity. Along 

 the anterior half of the ventral edge the inner plates are firmly 

 connected with each other, but for the rest slightly diverge up- 

 wards and backwards. They exhibit a very complicated system 

 of highly chitinised stripes curved in different manners and ana- 

 stomosing with each other, some of them forming very compact 

 and dark horn-coloured projections of the upper face and apparently 

 serving for a closer affixion of the organs to the genital parts 

 of the female. Through the neck-shaped part connecting the 

 organs with the body two narrow canals are seen penetrating 

 the organs, forming within the same several circumvolutions; 

 these canals represent the outer part of the „vasa deferentia" 

 or spermatic ducts 



Inner organs. — The alimentary canal consists of 3 prin- 

 cipal parts: a narrow, muscular oesophagus ascending almost 

 perpendicularly from the mouth, the intestine proper, and a very 

 short rectum opening just in front of the caudal rami. The 

 intestine proper exhibits two considerable dilatations, the anterior, 

 lying in the foremost part of the body, almost globular 

 in form, the posterior somewhat larger and more oval, both 

 defined by a well-marked median instriction, just above the great 

 adductor of the shell. From the anterior division of the intestine 

 2 slender coecal appendages are given off, each being received 

 between the lamellae of the corresponding valve (see PI. Ill, fig. 

 11) and running diagonally backwards to the infero-poste- 

 al corner. They generally exhibit a bright green colour, and 

 their walls are invested by large cellular bodies, probably secret- 

 ing a fluid for dissolving the aliments. 



Of a heart there is no trace to be detected, neither of any 

 distinct blood-vessels. 



The nervous system I have not been able to examine 

 in details, on account of the concealed situation of its cen- 

 tral parts. 



The inner genital organs considerably differ in structure in 



