40 MR. T. SCOTT ON -ENTOMOSTRACA 



Pontellklce. Second branch of the posterior antenutc longer than the prhiiary branch, 

 4-jointed. Mandibles stout, broad, furnished with papilliform teeth and elongate 

 tooth-like processes on the exterior angle ; mandible palp 2-branched, secondary 

 branch 3-jointed. Anterior foot-jaws like those- of Ithincalanns cornutus. Posterior 

 foot-jaws strong, 6-jointed, the two basal joints large. The first four pairs of swimming- 

 feet have both branches 3-jointed. Pifth pair in both sexes 1-branched, those of 

 the male dissimilar and adapted for grasping ; those of the female the same on both 

 sides, 3-jointed, the last joint produced into a large curved spiniform process. Ovisac 

 large. 



Heterocalanus serricaudatus, n. sp. (PL II. figs. 43-48; PI. III. figs. 1-7.) 



Length 1"15 mm. Body elongate, narrowly rounded in front, the postero-lateral 



angles of last thoracic segment rounded, and bearing several small spines. Anterior 



antennse longer than the body ; those of the female slender, 22-jointed, sparingly seti- 



ferous. The proportional lengths of the joints are nearly as follows : — 



11 ■ 11 . 5 ■ 7 . 6 . 10 . 5 ■ (i . 10 . 12 . 14 ■ 16 ■ 18 . 18 ■ 18 . 16 . 14 . 14 . 13 . 14 . ]2 . 3 

 1 2 3 4 5 6 7 8 9 10 11 IL' 13 14 15 16 17 18 19 20 21 22' 



The right anterior antenna of the male also 22-jointed, distinctly hinged between the 

 18th and 19th joints, the upper margin of the 18th joint serrate ; the 11th and 

 12th joints are small, the 14th, 15th, and IGth dilated. The general form of the male 

 riffht antenna somewhat resembles that of the Pontelliclce. Posterior antennae have the 

 secondary branches longer than the primary, 4-jointed, the third joint very small, im- 

 parting to the branch the appearance of being much constricted in the middle ; both 

 branches furnished with numerous non-plumose hairs. Mandible stout, broad, bearing 

 several small papillose teeth, and on the exterior angle three elongate tooth-like processes 

 and a short plumose seta. The basal part of the mandible palp is comparatively large, 

 and produced laterally to form the base of the secondary branch, which is 3-jointed. 

 Both branches are furnished with a number of non-plumose hairs (PI. III. fig. 4). Anterior 

 foot-jaws like those of Rhmcalaiius cornutus, short, obscurely 3(or 4 ?)-jointed. 

 Posterior foot-jaws strong, 6-jointed, the two basal joints large, the other four small, 

 subequal ; each of the fourth, fifth, and sixth joints bear interiorly a stout, elongate, 

 blunt-pointed spine, that of the fifth being much larger than those of the other two 

 joints ; the terminal joint is also furnished with six long plumose hairs. The first four 

 pairs of swimming-feet are 2-branched, both branches 3-jointed. The joints of the 

 inner branch of the first pair subequal ; the outer branch is without dagger-Hke spines 

 at the distal angles of the joints. The first joint of the inner branch and the middle 

 joint of the outer branch of the second, third, and fourth pairs are smaller than the other 

 joints, and the exterior distal angles of all the joints of the outer branches bear stout 

 dagger-like spines, which are finely serrate on both edges ; the last joint has an additional 

 and similar spine arising from an excavation on the lower half of the outer margin. 

 The terminal spines of the outer branches are finely serrate on the outer edge, except 

 near the base, which is plain ; the extremity of the terminal spines is slightly curved 



