new Parasitic Gopepods on Fish. 93 



mounted specimens), the thorax only shows as one ring, the 

 genital segment is proportionately much shorter, and the 

 anterior antenna?, though setaceous, appear to be only tri- 

 articulate. 



Gerstaecker separates the Dichelesthiina thus : — 



A. Abdomen with two large dorsal plates .... Anlhosoma, Leach. 



B. Abdomen without dorsal plates. 



a. Ambulatory leg suppressed Tucca, Kr. 



i Norton, Nordui. 

 Epachthes, Nordm. 

 Lernanthropus, Nordm. 

 Dicheksthium, Herni. 

 e. Posterior legs neither bigger than front nor 

 lamellar. 

 a'. Posterior antennae with chelifonn end- 

 claw. 

 a". All four pairs of limbs 2-branched. 



a'". Anterior antennae 8-jointed .... Lonchidium, Gerst. 

 b'". Anterior antennae 4-jointed .... Baculus, Lubb. 

 b". Only two first pairs 2-branched .... Philichthys, Stp. 

 b' . Posterior antennae with single end-claw. 

 a". Anterior antennae single, posterior 

 projecting. 

 a'". Only two pairs of limbs formed ; 

 genital segment five or six times 

 as long as head and thorax ; 



anterior antennae 6-jointed Clavellu, Oken. 



b'". All four pairs of limbs formed. 

 a*. Anterior antennae 15-jointed ; 

 second to fourth legs 2- 



branched, 1-jointed Ne?nesis, Roux. 



b*. Anterior antennae 6-jointed; all 



limbs 2-branched. .' Cycnus, Edw. 



c 4 . Anterior antennae 3-jointed ; only 

 second pair 2-branched, the 



others stump-like Pseudocycnus, Hell. 



b". Anterior antennae with hooked basal 

 joint; the posterior short, with three 



claws Eudactylina, Bened. 



c . Posterior antennae without end-claw ; 

 the point provided with hairs. 

 a". Anterior antennae 10-jointed ; true 



legs single-jointed Lamproglena, Nordm. 



b" . Anterior antennas 5- join ted ; true 



legs 3-jointed Donusa, Nordm. 



In accordance with the two new genera which I have 

 described, the classification of the latter portion has to be 

 somewhat altered, as follows : — 



b' . Posterior antennae with single end-claw. 



a". Anterior antennae single, posterior 



projecting. 



a" . Only the two anterior pairs of 



limbs formed ; genital segment 



Ann. & Mag. N. Hist. Ser. 7. Vol. ii. 8 



