PACKARD.] PHYLLOPODS OF NORTH AMERICA. 315 



"The structure of the carapace is the same as in Limnadia Hermanni, 

 the surface being covered with minute dots or punctuations. 



"This species differs from the two others in the shape of the carapace 

 and in having the setse of anteunse and tail plumose. 



"iZ«&.— St. Domingo, West Indies; M. Salle, Mus. Brit." (Baird.) 



Family APODID^ Burmeister. 



Head and body in front broad and iiat, shovel-shaped ; carapace broad 

 and fiat; the body cylindrical, few or numerous segments extending 

 beyond the carapace; antennse small, 2d pair minute, sometimes want- 

 ing; labrum large, broad, flat; feet numerous, usually 63 pairs; with 

 a large coxal, maxilla-like basal lobe forming gnathites; beyond five 

 subjointed endites ; the 2-4th endites in 1st pair of feet very long and 

 slender, especially the 5th ; gill pear-shaped or bottle-shaped ; flabellum 

 triangular, simple ; the 5th endite of the 1st pair of legs is sometimes 

 nearly as long as the body, the 11th pair bearing egg-sacs, and in the 

 male having the genital outlet. Behind the 11th pair two of the abdomi- 

 nal segments bear each six pairs of appendages, there being many more 

 ai3j)endages than segments to the abdomen, while a variable number at 

 the end are without appendages. Telson cylindrical, either short or 

 euding (in Lepidurus) in a long paddle-like outgrowth. A pair of long 

 filiform jointed caudal appendages. Larva a nauplius. 



Synopsis of the genera. 



Telson ending in a long j^addle-shaped outgrowth Lepidurus 



Telson short, cylindrical, simple- Ajnis 



Genus LEPIDUEUS Leach. 



Plates XV, figs. 2, 2a, 3; XVI, figs. 1, la, lb; XVII, XXI, figs. 1-6, 9, 11. 

 Jj^idurus Leacli. Diet, des Sc. Nat. I, 259. 1816. 



Body rather deeper, more rounded than in Apus ; the carapace longer 

 in proportion to the body than in Aptis. Frontal doublure much as in 

 Apus J but with a rather prominent tubercle at the base of the hypostoma, 

 while the latter is much larger than in Apus. Eyes as in Apus^ but the 

 tubercle behind the eyes is oblong-oval, instead of round, as in all the 

 species of Apus I have seen. Antennae much as in Apus. Mandibles as 

 in Apus, with the same number of teeth ; but the dorsal mandibular 

 transverse tubercle on the carapace is larger ; the maxillse also as in 

 A-pus. The endites of the 1st pair of legs are very short, the outer ones 

 in some species scarcely projecting beyond the edge of the carapace ; 

 there are about twelve subjoints in the 5th or longest endite, and the 

 ends are usually (not always) rather bluut. The flabellum is very small 

 compared with that of Apus, being narrow, triangular, the distal end 

 acutely pointed, the gill or gill sac itself much as in Apus. In the suc- 

 ceeding pair of legs there are no good generic difterences between Apus 

 and Lepidurus, though endites 2-5 are inclined to be rather the longer 

 in Lepidurus. Gnathobases or coxal lobes much alike in the two genera. 



In comparing the 10th pair of feet of Apus and Lepidtirus no generic 

 diflerences are to be observed, while the 11th pair, bearing the ovisacs, 

 do not essentially diiier in the two genera, but aftbrd excellent specific 

 characters ; however, the ovisacs in Lepidurus are considerably larger 

 and deeper than in Apus. 



