530 PROCEEDINGS OF TTTE NATIONAL MWEUM. vol. xxvin. 



SYSTEMATIC. 

 niSTORlCAIv. 



'Pile lirst which riui really be ciiiled a elassiHcation of the parasitic 

 c()p(^pods was made by Buriueister in 1838 and included only 28 out of 

 the SO and more genera known at the present day. 



The group was divided into families on the basis of th(^ presence 

 and structure of the antenna^ and segmented feet. 



Each family was divided into genera upon a ditiercnt basis, that for 

 the Caligidsi; consisting in the presence or absence of eyes and the 

 structure of the fourth thoracic feet. 



The next important classification was ])y Milne Edwards in his great 

 work on tlie Crustacea in 1840. lie raised the munlxn" of genera of 

 these parasites to 35 and divided them tii'st according to tla^ fusion of 

 the head and thorax, and the structure of tiie antenna\ They were 

 tluMi subdivided l)y the presence or al)sence of dorsal plates on the 

 free thoracic segments, while the Caligidte were classified l)y the 

 structure of tlie fourth legs. This resulted in throwing all the forms 

 with dorsal ])lates on the thorax into the Pandariiuv, irrespective of 

 their relations in other particulars. 



As thcn-e wM^r(> only t> genera known at that time in thi' C'aligida', 2 

 of which, ('iHil/nnis and Xogcupis, were spurious, such a dixision 

 answered well enough, and it located each genus just where it stands 

 at the present time. 



A third classification was published ])y Steenstrup and Liitken in 

 1801, and by Nordmann in 1864, the two being identical. 



They increase the number of genera to 68, of which 20 belong to 

 the Caligidtv; they divide them first according to the structure of the 

 ^gg sacks and the arrangement of the eggs. 



The second subdi\ision is on the basis of the degree of fusion 

 between the head and thorax, and on the presence or absence of a 

 carapace. In the family C-aligiche the classification is based on the 

 structure of the fourth feet, the presence of dorsal plates on the free 

 segments of the thorax, and the presence of lunules on the frontal 

 plates. 



Helhu', in 1865, adopted practically the same classification, but gave 

 a much more elaborate analysis of the genera belonging to the Cali- 

 gida?, which he increased to 26 in munb(M'. 



For this analysis he makes use of (1) the structure of the rostrum 

 and "palps"' (second maxilUv); (2) the degree of fusion between the 

 head and thorax; (8) the presence of dorsal plates on the free thorax 

 segments; (4) the presence of lunules; (5) the structure of the fourth 

 thoracic feet. 



In the following j-ear, 1866, there appeared the first number of 

 Bronn's Thierreich, in the fifth volume of which, under the Copepoda, 



