344 LECTURE XVI. 



Order AMrniPODA. 



Abdomen terminated by saltatorj or natatory appendages : thoracic 

 limbs unequal, with basal vesicular branchial appendages. 



Genera Amphitho'e^ Talitrus, Gammarus^ Hyperittj Phronima, 

 Vibilia. 



Division PODOPHTHALMA (with eye-stalks, and a cephalo- 

 thoracic carapace). 



Order Stomapoda. 



BranchicB exposed, usually tufted, attached to the abdominal and 

 (in some) to a few of the thoracic limbs : rarely abortive. 



Genera Phyllosotna, Amphion^ Mysis, Lucifer, Cynthia, Alinia, 

 Squilla. 



Order Decapoda. 



BrancMcB in cavities at the sides of the thorax : first two thoracic 

 limbs serving as jaws : the other five chelate, uncinate, with the last 

 pair sometimes lamellate. Crust commonly calcified. 



Tribe Macroura. (Abdomen long, with lamelliform limbs, and 

 terminated by a natatory appendage. An- 

 tennae long.) 

 Genera Penceus, Alpheus, Caridina, Hippolife, Palcemon, Gebia, 

 Callianassa, Crangon, Nephrops, Astacus, Homarus, Palinurus, 

 Scyllarus, Galathea. 



Tribe Aiiomoura. (Abdomen moderately long, not a natatory organ. 



Antennae long.) 

 Genera Pagurus, Birgus, Porcellana, Remipes, Ranina, Homola, 

 Lithodes, Dromia, Dorippe. 



Tribe Brachyura. (Abdomen short, bent beneath the thorax. 



Antennae short.) 

 Genera A. Matuta, Calappa, Leucosia ; B. Pinnotheres, Grapsus, 

 Gelasimus, Ocypoda, Gecarcimis, Thelphusa ; C. Portunus, Cancer; 

 T). 3Iaia, Inachus. 



LECTURE XVI. 



INSECTA. 



Although spontaneous locomotion is the peculiar attribute of the 

 Animal Kingdom, we have seen that the lowest members, the Zoophy- 

 tes as they were termed, were, for the most part, fixed and rooted 

 like plants : we have seen that the first manifestations of locomotion 



