2306 CRUSTACEA. 



Tribus III. LIMNADIOIDEA. 

 Fam. I. LIMNADIDJE * 



G-. 1. LlMNADIA, Ad. Brongniart. — Caput vix rostriforme, dorso tuberculum pyri- 



forme gerens. Pedes toti foliacei. Abdomen extremitate appendicibus acumi- 



natis quatuor armatum. 

 G. 2. Cyzicus, Audouin.f — Caput instar rostri productum, dorso non tuberculi- 



ferum. Pedum pares numero ferme 21, foliacei. Abdomen fere ac in Lim- 



nadid. 

 Gr. 3. Limnetis, Loven-l — Antennae internse 2-articulatse. Cauda brevis, truncata, 



appendicibus facie inferiore destituta. Pedum pares 12. 



We add a few words on the above groups. The Artemioidea are 

 closely related to the Mysidea ; and if we look at this relation, we 

 shall appreciate the propriety of uniting together in one group all the 

 genera which we have so assembled. This relation is apparent in the 

 general form of the body, the extended abdomen, and the caudal 

 appendages. These appendages are simply two lamella, and the 

 abdomen has the normal form, although abnormal in its number of 

 articulations, while in Limnadia, Apus, and the allied, the abdomen is 

 of a very different character. The carapax of Nebalia is much like 

 the same in the Mysidse and Erichthidse, while the divided cephalo- 

 thorax of Chirocephalus without a carapax, is but a step removed from 

 other Mysidea. The Cyclopoidea, which of all Entomostraca are 

 nearest to the Mysidea, have no free carapax, but instead an annu- 

 lated cephalothorax analogous to that of Artemia and Chirocephalus, 

 although with fewer segments. 



Again, the relation of both Nebalia and Chirocephalus to the Mysi- 

 dea is seen in the presence of pedunculated eyes, which is a remnant 

 of the Podophthalmia structure in this lower order of Crustacea. 



* Apusiens (in part), of Edwards, Crust., iii. 353. 



| Audouin, Ann. de la Soc. Entomologique, vi. 1837, and Bulletin, Feb., 1837; 

 Estheria, Kiippel, Mus. Senkenbergianum, ii. 119, 1837 ; Isaura, Joly, Ann. des Sci. 

 Nat. [2], xvii. 293, 1842. 



X Kbngl. Vet. Akad. Handl., for the year 1845, Stockholm, 1847, 427. Hedessa oi 

 Lievin (see Branchiop. der Danziger Gegend. Ein Beitrag. zur Fauna der Provinz 

 Preussen, 4to with eleven plates, Danzig, 1848, and Arch. f. Nat. 1849, 327), is very 

 near Limnetis. 



