Page:Transactions NZ Institute Volume 15.djvu/128
footjaws broad, setæ numerous; posterior pair much elongated, terminal portion five-jointed, and furnished with several setæ of moderate length. Five pairs of swimming feet, all two-branched, and each branch of the first four pairs three-jointed and almost similar; fifth pair with both branches three-jointed in the female, but outer branch two-jointed in male, with a long terminal curved (apparently prehensile) claw, inner branch somewhat rudimentary, one-jointed. Ovisac single, borne in front of the abdomen.
It is with some hesitation that I advance this new genus, but as the chief systematists who have studied the Calanidæ treat the structure of the inner branches of the swimming feet as of primary importance in the classification of the genera, no other course was open to me. The genus belongs to the same section as Isias (Boeck), and Centropages (Kröyer). The former is its nearest ally, but differs in having the inner branch of the fifth pair of feet in the female one-jointed, while in the male the outer branch consists of two, and the inner of one or two joints. In Centropages, the strong bristles on the anterior footjaws point to its affinity with the sub-family Pontellinæ, and the outer branch of the fifth pair of feet in the male is developed into a powerful grasping claw on the right side only, while the inner branch is normally three-jointed.
1. Boeckia triarticulata, sp. nov. Pl. VI., fig. 1.
Body elongated, rounded above, last thoracic segment produced into a strong spine on its infero-posterior margin. Anterior antennæ almost as long as the body: that of the male on the right side swollen in the middle, hinged between the 19th and 20th joints, and bearing denticulated plates on the inner face of the 18th and 19th joints above, and on the 20th joint below the hinge; spines and setæ rather few. Fifth pair of feet in the female somewhat similar to preceding pairs, but with the middle joint of the outer branch produced internally into a strong toothed spine (in this respect resembling to some extent Centropages typicus), inner branch rather reduced in size; in the male the outer branch is distended and two-jointed, with a long terminal curved claw, which is longer and more slender on the left than on the right side. Caudal segments about as long as last abdominal segments, and bearing five densely plumose rigid setæ, which are shorter than the abdomen.
Length (including caudal setæ) 1⁄10 inch; spread of anterior antennæ, 1⁄7 inch.
Hab. This interesting species was obtained in shingle-pits (fresh water) at Eyreton, in the North Canterbury District, by Mr. Chas. Chilton. Most of the specimens are reddish in colour, but the colouration is very variable both in intensity and localization.