88 THE VOYAGE OF H.M.S. CHALLENGER. 



branch of the posterior antennse have but three setae at the apex ; the inferior eyes are 

 quite small, This sub-genus may include some species referred to Hemicalanus. 



" 2. Pontellina. — -Antennse of second pair having five setae at the apex of the anterior 

 or smaller branch ; head either side unarmed. 



"3. Pontella. — Antennse as in the last ; head either side armed with a reversed spine. 

 The Pontia atlantica of Edwards is of this kind. In this division the second of the 

 caudal setae is considerably longer (one-fourth at least) than the others (in most, if not 

 all cases), which is not true of the preceding sub-genus Pontellina." 



Again, Sir John Lubbock 1 has proposed two new genera — Labidocera and Monops — ■ 

 with three sub-genera, Labidocera, Ivella, and Iva. The generic and sub-generic defini- 

 tions are as follows : — 



" Labidocera. — Kostrum furcatum; antenna antica maris dextra geniculans, tumida, 

 lamellis lobulisve dentatis instructa. Oculi superiores duo. Oculi inferiores nulli ? 

 Cephalothorax 7-articulatus. Pes posticus maris dexter, prehensilis. Abdomen maris 

 4-articulatum, feminae 2-articulatum. 



" Sub-genera : — 1. Labidocera. — Antenna antica maris dextra duabus serratis lamellis 

 instructa. Spina prehensilis, parva, rigido crini similis. Pes thoracicus quintus sinister, 

 parvus, ramum internum 2-articulatum, ad apicem annulatum gerens. 2. Ivella. — 

 Antenna antica maris dextra tribus dentatis lobulis instructa. Spina prehensilis, magna. 

 Pes thoracicus quintus sinister, magnus, fortis, ad apicem acutus et corneus, ramum 

 internum non gerens. 3. Iva. — Antenna antica maris dextra quatuor dentatis lamellis 

 instructa, tumidissima. Spina prehensilis, maxima, annulata. Pes thoracicus quintus 

 sinister, magnus, ad apicem tumidus, papillosus. 



" Monops. — Kostrum furcatum. Antenna antica maris dextra geniculans, tumida. 

 Oculi superiores nulli. Oculus inferior unicus. Pes posticus maris dexter crassus 

 prehensilis." 



The characters, however, upon which these divisions are based, though useful as 

 affording specific distinctions, utterly break down when applied to larger groups. It has 

 been already shown that Dana's two species of Calanopia belong really to distinct 

 genera, and would scarcely have been brought together if the characters of the mouth- 

 organs and feet, as well as the eyes and antennae, had been taken into account. 2 For the 

 same reason, Sir John Lubbock's genera and sub-genera appear to me quite untenable. 

 The restriction of the generic term Pontellina as proposed by Dr. Claus, to species having 

 a rostral lens, lateral upper eyes, lateral spines on the head, and a six-jointed apex to the 

 posterior foot-jaw, will, I suspect, also be found impracticable ; at any rate if the 

 subordinate character of a three-jointed inner branch to the first foot is to be taken in 



i Ann. and Mag. Nat. Hist, March, August, and September 1853. 



2 It will be seen that though I adopt this term Calanopia for a genus of which Calanopia ellipti:a, Dana, is the type, 

 I depend for its diagnosis on characters entirely distinct from those originally proposed. 



