94 Transactions. — Zoology. 



footjaws broad, setae numerous; posterior pair much elongated, terminal 

 portion five-jointed, and furnished with several seta? of moderate length. 

 Five pairs of swimming feet, all two-branched, and each brauch 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 some- 

 what 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 Calamdm treat the structure of the 

 inner branches of the swimming feet as of primary importance in the classi- 

 fication of the genera, no other course was open to me. The genus belongs 

 to the same section as Isias (Boeck), and Centropages (Kroyer). 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 

 Pontellince, 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 triarticidata, sp. nov. PI. VI., fig. 1. 



Body elongated, rounded above, last thoracic segment produced into a 

 strong spine on its infero-posterior margin. Anterior antennas 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 setae 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 tyjricus), 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 abdo- 

 minal segments, and bearing five densely plumose rigid setae, which are 

 shorter than the abdomen. 



Length (including caudal setae) T ^ inch ; spread of anterior antennae, 

 \ inch. 



Hah. 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. 



