H22 CRUSTACEA. 



ACARTIA TONSA. 



Fr&ns rotundaius. Cephalothorax posticd obtusus, 6-articulatus, capite 

 discrete. Antennce anticce multiarticidatce, rectce, apicibus fronte non 

 anterioribus, setis plerumque brevibus, paucis longiusculis (3-4 articulos 

 simul sumtos longitudine cequantibus) . Antennce posticce pertenues, 

 rarno uno triplo longiore. Styli caudales perbreves. 



Front rounded. Cephalothorax obtuse behind, six-jointed, head sepa- 

 rate, posterior segments three, and subequal. Anterior antennae 

 many-jointed, straight, as long as the cephalothorax, the tips not in 

 advance of the front, near the base bent at an angle, and from 

 thence straight, apical joint minute; setae mostly short, apical and 

 two or three others nearly as long as one-fourth the antenna ; pos- 

 terior antennas slender, one branch three times the longer. Caudal 

 stylets very short, but a little oblong. 



Plate 79, fig. 4 a, enlarged ; a', extremity of anterior antenna, more 

 enlarged; 6, posterior antennas, ditto; c, palpus of mandible; d } max- 

 ilL; e, maxilliped; /, first pair of feet; g, eyes. 



Collected in Port Jackson, New South Wales, March, 1840. 



Length, one-eighteenth of an inch. Colourless. The front of the 

 head is scarcely at all prominent between the anterior antennae. 

 These antennae at the fourth joint bend directly out, and each falls 

 slightly back of a common straight line. At the bend there is a 

 longish seta, another on the fifth joint from the apex, one a little 

 shorter on the anterior side of the second, and a much shorter one 

 on the posterior side of the same joint. The setae of the last and the 

 penult joint are nearly equal, that of the posterior antepenult is of the 

 same length or a little longer, but the anterior antepenult, and both on 

 the joint next preceding, are quite short. The third joint from the 

 apex is longer than the fourth or second. The caudal setae are not 

 quite as long as the abdomen. The length of the abdomen little ex- 

 ceeds one-third the cephalothorax. The eyes are situated on a single 

 quadrate spot of pigment, which is rather large. 



