some Entomostraca. 17 



posticarum ramus lateralis multiarticulatus, pyramidatus, setis 

 longis. Mandibulae palpo magno rami's valde inaequis. Pedes 

 natatorii primi paris ramis 3 et 2 ?-articulatis. Pedes quarti 

 paris ramis 3-articulatis. Abdomen curtum, 2 ?-articulatum. 

 Styli caudales breves. 



The anterior antennas are considerably longer than the body ; 

 the hairs all along the middle part are small, but some near the 

 apex are very large. The posterior penultimate is the longest, 

 then two at the apex, and one attached to the fourth segment, 

 counting from the apex. Length "17. 



The posterior antennae are remarkable for the form of the lateral 

 branch, which is multiarticulate, tapering and clothed with long 

 hairs. Length -033. 



The palpus of the mandible is also of an unusual shape. In- 

 stead of consisting, as usual, of a large basal portion, bearing at 

 the apex two equal short branches, in this species one branch is 

 inserted at the side of the basal part, and is much smaller than the 

 other. Length -033. 



The second pair of maxillae are '015 in length, and the maxilli- 

 peds -052, 



The first pair of natatory legs are '026 in length ; the outer 

 branch is three-jointed ; the inner, I believe, has two segments, 

 which are well marked in the second pair of legs, but in the first 

 are very indistinctly separated. The fourth pair is "03 in length, 

 and both the branches have three segments. The fifth pair ap- 

 peared to me to be altogether absent. 



The abdomen is short, and in my specimen most of the caudal 

 bristles appeared to have been broken off. 



Collected in the Bay of Biscay. 



PI. V. figs. 1 to 6. 



Calanus hrevicorn'is, n. sp. 



Frons elongata, angusta, rotundata, stylis longis. Cephalo- 

 thorax postice obtusus, 5-articulatus articulis posticis sub- 

 aequis. Antenna antice cephalothoracis longitudine, fere 

 rectae, fronte posteriores, setis brevibus, articuli tertii lon- 

 giore^ postica penultima et antepenultima longis, anticis bre- 

 vibus, antica penultima articulo duplo longiore. Setae cau- 

 dales raediocres. 



The front is produced '01 inch beyond the base of the antennae ; 

 the frontal stylets are long, and rise just in front of the antennae. 



VOL. IV. N. S. PARTI. — OCTOBER, 1856. C 



