CYCLOPOIDEA. 1Q43 



on the under side of the head, distinguishes Pontella, Acartia, and 

 Catopia from the other genera ; and a geniculation in the right male 

 antenna of the first pair, characterizes Pontella, 'Catopia, Candace, 

 Diaptomus, Hemicalanus. The presence of the inferior eye, with com- 

 monly the geniculating right antenna, may, therefore, distinguish one 

 subfamily, Pontellinm, from the other related, Calanince, in which the 

 inferior eye does not exist. The transitions among the genera of the 

 two groups thus instituted, are, however, very gradual. An enlarge- 

 ment of the posterior thoracic legs in the males, and the existence of 

 a prehensile form in the right leg of the pair is found in all the 

 species that have the geniculating joint in the right male antenna. 

 But there are two genera in which this enlarged posterior pair of legs 

 exists, without the geniculating joint. One of them, TJndina, closely 

 resembles Calanus in most characters, but has a slight angle in the 

 antennae, not far from its middle, and probably this organ has the 

 power of flexion, in the same manner as when a geniculating joint 

 exists; the genus, therefore, is intermediate between the Calaninae 

 and Pontellinae. The other, Euchmta, also, has nearly the habit of 

 Calanus ; although, differing from all the other Calanidae in its beak, 

 the long setae of the female antennas, and the anterior feet. Cala- 

 nus and Euchaeta are the only genera in which the feet of the first 

 pair are stouter than the maxillipeds, the maxillipeds being generally 

 the larger pair, and the first pair of legs in Pontella being sometimes 

 even rudimentary. 



A single genus, Oiihona, differs widely from the others in having 

 the abdomen very long linear, not shorter than the cephalo-thorax, 

 and the maxillae and mandibles of peculiar form, and it may be the 

 type of a third subfamily, Oithonince. 



Besides these, there is another subfamily quite distinct from the 

 above, in having the antennae of the second pair prehensile or mono- 

 dactyle. It includes the genus Notodelphys of G. J. Allman.* The 

 probable relation of the Notodelphys to the Calanidae in the maxilli- 

 peds, maxillae, and mandibles, will be seen on comparing these organs 

 with those of the other Calanidae ; and to aid the comparison we have 

 copied on Plate 71 the figures of these parts by Allman. Fig. 117 is 

 the mandibular palpus; 118, maxillary palpus; 119, maxilliped; 120, 

 first pair of legs. Figure 116 of the same Plate, represents the 



* Ann. and Mag. Nat. Hist., xx. 1, PI. 1 and 2; and Baird's Brit. Entomost., 1850, 

 237, PI. 30. 



