CLASS I. CUUSTACEA. 95 



and une(iiial: tail broad; the intermediate lamella elongate-trian- 

 gular. 



Sp. 1. Ax. Stlrync/ius. Rostnmi margined, the middle carinatcd: thorax he- 

 hind the rohtnim, with two elevated abbreviated lines n<jtched behind. 



Axius Stirynchiis. Ixach, Trans. Linn. Soc. xi. 3*3. — Si'pp. tu EncycL 

 Brit. i. A20.—MaL Fodoph. Brit. tub. 33. 



Inhabits the British sea. 



Stiups 2. Exterior InnicUa of the tail bipartite : external antenna: with a 

 spine-shaped s(piame at the lir.^t joint ot" the peduncle: anterior pair 

 of legs didactyle. 



* Ei/es suhglobose, not thicker than their ped unites. 

 Tlie coxaj of the third pair of legs of the female, of the fifth pair 

 of the male, ])erforated. These perforations are for the passage of 

 the semen and of the eggs ; and although placed differently in other 

 genera, yet they serve the same functions. 



Genus SG". ASTACUS. Leach's MSS. 



Abdomen with the sides of its segments obtuse: middle tail lamella com- 

 posed of one piece. 



Sp. 1. Ast. (jammarus. Rostrum on pach side with four teeth, and with 

 one on each side of its base. 



Cancer Gammarus. Linn. S^/st. Nat. \. lO.'iO. AstacusGanmiarus. Pewn. 

 Brit. Zool. iv. O.pl. 10. Astacus marinus. Fabr.Supp. Ent. Si/st. 406. 

 Latr. Gen. Crust, et Insect, i. 51. Astacus Gammarus. Leach, Edin. Eih- 

 cycl. vii. 308. — Trans. Linn. Soc. \'h 34 1. — Snpp. to Enci/cf. Brit. i. -120. 

 This species, wduch is the counnon lol)stcr of our markets, inhabits 

 deep clear water at the foot of rocks which hang over the sea. They 

 breed during the early sunuuer months, and are very prolific, Baxter 

 having comiited no less than 12,414 eggs under the abdomen. In 

 warm weather they are very active; they have the power of spring- 

 ing backward in tile water to a most astonishing distance into tlieir 

 holes in the rocks, as has been frequently observ ed by naturalists of 

 credit. Their food consists of dead animal matter, and, it is said, also 

 ofsea-weed. The female is stated to deposit her eggs in the sand, but 

 tiie young state is not known. 



The common lobster inhabits the European ocean. It is found in 

 very great abundance in the North of Scotland; but is nuich more 

 common on the coast of Norway, from whence the London markets 

 are for the most part supplied. 



Genus 27. POTAMOBIUS. Leach's MSS. 



Abdomen with the sides of its segments sharp : n\iddle tail lamella bi- 

 partite. 



Sp. 1. Fot.Jiuviatilis. Rostrum laterally dcntated, the base with one 

 tooth on each side. 



Cancer Astacus. Linn. Sysl. ]S\i(. 1. 1051. Astacus astacus. Pcnn. 



