282 zooLoar. 



This suborder presents a beautiful series of increasingly 

 complex forms, as we ascend from Limnetis to Branehipus. 

 In Limnetis the bivalve shell encloses the ani- 

 mal, and is the size of a small flattened pea. 

 There are from ten to twelve feet -bearing 

 segments. L. Gouldii Baird (Fig. 238) is very- 

 rare in Canada and Xew England. The sheU 

 of Limimdia is thin, oval, and there are from 

 eighteen to twenty-six feet-bearing segments. 

 L. {Eulimnadm) Agassizii Packard (Fig. 239) 

 inhabits small pools in Southern Xew En- 

 gland. The sheU of Estheria (Fig. 241, Es- 

 240 -F re- ^'''^"''' Selfragei Packard) is sometimes mis- 

 leg of male ^<a«- taken for that of the fresh -water mollusks 

 ™«. a, hand; b, Vyclos and Pisidium. The males of the fore- 

 end of body. going genei-a have the first pair of feet modi- 

 fied to form large claspers (Fig. 240). 



In Apus the abdomen projects beyond the large carapace, 

 and ends in two long many-jointed appendages. There are 

 about sixty pairs of feet, each foot 

 divided into several leaf -like lobes, 

 wherein respiration is carried on. 



Tliese Phyllopods usually swim upon 

 their backs, as in the species of Bran- 

 ehipus. The females chiefly differ 

 from the males in the presence of an „ 



, . , ,1 , , . Rg. 241.— Shell of £i!M«7M 



orbicular egg-sac on the eleventh paar Selfraga, enlarged three 



of feet, the sac being a modification of ^' 

 two of the lobes of the feet, and containing bat a few eggs. 

 Apns wqualis Packard (Fig. 242, Fig. 244 A, represents the 

 larva of a European Apus) inhabits pools in the western 

 plains. Lepidurus differs from Apm in having the telson 

 spoon-shaped instead of square. L. Couesii Packard (Fig. 

 243) occurs on the Rocky Mountain plateau in Utah and 

 Montana. It is an interesting fact in zoo-geography that 

 there are no species of Apus and Lepidurus east of the west- 

 em plains. Apus has been found by Siebold to reproduce 

 parthenogenetically. 



The various species of Branehipus and Artemia have no 



