356 M. R. Leuckart on the Genus Notopterophorus. 



a basal joint, upon which two branches of several joints, but 

 otherwise differently developed and destined for different pur- 

 poses, are inserted. One of these branches, which is turned 

 inwards, appears to be a swimming-foot. It consists of only two 

 flattened joints, of which the apical one is somewhat the larger, 

 and is furnished on its sharp margin with a number of long 

 bristles. The other, longer, branch is formed of four cylindrical 

 joints, which gradually diminish in size towards the extremity. 

 Instead of the long swimming bristles, there are, on this, shorter 

 and stiffer spines, especially on the terminal joint, where these 

 at the same time attain their greatest development. These 

 structures are evidently better adapted for pushing ; they may 

 do good service in creeping. 



As regards the wing-like processes of the thoracic segments, 

 these (figs. 1 & 2) appear to be folds, and not separate, inde- 

 pendent appendages. They are therefore to be compared less 

 with the wings of insects than with the laminar processes so 

 often occurring in the Parasitic Crustacea ; although, as already 

 remarked, they differ from these in their position. The two 

 middle segments of the thorax each bear two such laminse, to the 

 right and left, whilst the anterior and posterior segments are 

 furnished with only a single leaf, which is curved to form a 

 furrow, as if here the two lateral leaves, touching each other at 

 an angle, had become fused together at their inner margins. 

 The concavity of the anterior leaf is turned backwards ; that of 

 the posterior one, on the contrary, is directed forwards. At the 

 same time the laminae gradually become broader as they depart 

 from the base, so that the margins overlap, and the space en- 

 closed by them becomes limited on all sides. The anterior leaf 

 stands most perpendicularly ; whilst the posterior one is most 

 inclined, but at the same time is the longest. The free margins 

 of the leaves are usually (the posterior angle of the third leaf 

 mbst constantly) furnished with one or more small points, but 

 never with such long and beak-like teeth as are represented in 

 Costa's figure. 



Of the five segments of the abdomen, the first three gradually 

 increase in length, whilst the last two again become shorter. 

 The total length of the abdomen is nearly the same as that of 

 the thorax, but its thickness is less than that of the thorax even 

 at the first segment (which, however, is not counted as a seg- 

 ment by Krohn), and from this gradually becomes less to the 

 apex. There are no appendages upon the two styles represent- 

 ing the furca, which include the anus between them, and are 

 furnished at the extremity with three minute tubercles. 



In the specimen figured by Krohn (fig. 3), we observe in the 

 last segment of the thorax, immediately below the leaf attached 



