160 Mr. J. Lubbock on two new species 0/ Calanidae. 



apical segment, being apparently replaced from the Ist to the 

 12th segments inclusive (counting from the apex) by 

 3rdly. Ordinary, cylindrical tapering hairs, and 

 4thly. By transversely wrinkled hairs. These two last gra- 

 dually pass into one another, and though generally perfectly 

 distinct, yet it is sometimes difficult to know to which form the 

 smaller hairs belong. And 



5thly. Flattened lanceolate hairs. Hairs of this shape are 

 represented on the antenna of a Calanus quinqueannulatus in 

 Gaimard's ' Voyage en Scandinavie,' but I do not remember ever 

 to have seen similar ones on any other animals. 



The normal arrangement of these hairs is three on each seg- 

 ment, all on the inner side. I have already observed, however, 

 that the short down is, when present, on the outer side. The ex- 

 ceptions to this rule are the three apical segments, of which the 

 terminal bears seven hairs ; and the other two have each one on 

 the outer side in addition to those on the inner. These two hairs 

 (PI. VII.) are very conspicuous in Cetochilus septentrionalis, Cala- 

 nus communis, and Oithona setiger, Dana, and are also present 

 in Pontella, Acartia ?, Dana, Catopia, Dana, Caudace, Dana, 

 Undina, Dana, Euchata, Dana ; in short, I believe they will be 

 found throughout the family. The plumose, wrinkled and ordi- 

 nary hairs appear often to pass gradually into one another, the 

 secondary setae becoming further and further apart, and the 

 wrinkles less and less distinct ; they also often replace one 

 another, the plumose prevailing on the apical and the twelve 

 basal,, and being almost entirely absent on the intermediate seg- 

 ments. On the other hand, the lanceolate hairs are much more 

 constant and definite in form ; there is not one on every seg- 

 ment, but wherever a segment is provided with its three hairs, 

 one is lanceolate, and to this rule 1 know of no exception. The 

 other two are generally (in that part of the antenna containing 

 the second and eleven following joints to which our attention is 

 now chiefly directed) one ordinary and one wrinkled, sometimes 

 however two wrinkled or two ordinary. I have already remarked 

 that ea«h segment, except the three anterior, is normally pro- 

 vided with three hairs, the apical with seven, and the second and 

 third with four each. The number is often less, but never more 

 than this. In the ordinai-y unswollen antenna, two of the hairs, 

 one of which is the lanceolate, are attached to the upper end, and 

 one to the middle of each segment, but in the swollen prehensile 

 antennae they are all found at the apex. 



In the females, and in the left antenna of the males, we find 

 on the eleventh segment a strong hair larger than the rest, and 

 evidently homologous with the hair marked {u) on Pontella 

 Bairdii. This again as evidently represents that marked («) on 



