some Entomostraca. 23 



Collected in the Atlantic Ocean, N. L. 37° ^0' to 12° 21', W. L. 

 14° 30' to 25°. 



I have called this species after Professor Dana. The Atlas of 

 his great work on Crustacea which has recently appeared is an- 

 other proof of his talents and industry. The high price of it is the 

 more to be regretted, as it is almost indispensable to every one 

 who would study Crustacea. 



Undina longipes, n. sp. 



Maris. — Frons quadrata. Cephalothorax 5-articiilatus, articulo 

 ultimo breviore, postice rotnndatus. Antennse anticsecor- 

 pore breviores setis brevibus, setd articuli secundi (tertii ?) 

 longiuscula, flexa, setis apicalibus articulo longioribus, setis 

 penultimis subaequis, articulo longioribus, seta antepenultima 

 posticd aliis longiore. Abdomen 4-articulatum. Styli cau- 

 dales 2-articulati, setis 5, secunda fere duplo longiore. 



The shape of the cephalothorax and the form of the apical hairs 

 of the anterior antennse are quite sufficient to distinguish this 

 species from all that have been hitherto described. The shape of 

 the fifth pair of legs is also peculiar. 



Anterior antennae '075 in length. 



The second pair of antennce have the accessory branch longer 

 than the organ itself, and besides the usual four hairs belonging 

 one to each of the four small intermediate segments, there are four 

 or five others, signs of a tendency to the separation of other seg- 

 ments. 



The second pair of maxillce are like those of Calanus, and quite 

 different from those of the other species of Undina which I have 

 seen. 



The maxillipeds are small, but like those of Calanus. 



The first pair of legs are '018 in length; the rami are both 

 three-jointed. 



The fourth pair are larger, '03 in length. 



The fifth pair are much larger, being *1 in length. The figure 

 will give a better idea of their form than a description could 

 convey. 



The abdomen is four-jointed, the segments being nearly equal in 

 size. The caudal lamellae are two-jointed, and bear five hairs, of 

 which the second is nearly twice as long as the rest. 



Total length '1. 



Collected in the Atlantic, 12° 20' to 8° 30' N. L., 25° to 23° 



