CLASS I. CRUSTACEA. 
95 
and unequal: tail broad; the intermediate lamella elongate-trian- , 
gular. 
!’• 1 ■ Ax. Stirynchus. Rostrum margined, the middle carinated: thorax be- 
nnd the rostrum, with two elevated abbreviated lines notched behind. 
jV S . Stirynchus. Leach, Trans. Linn. Soc. xi. 3-13. — Sapp, to Lucy cl. 
■'■it. i. 4a 0 . — Mai. Podoph. Brit. tub. 33: 
11 nilnts the British sea. 
ir.rs 2 . Exterior lamella of the tail bipartite : external antenna with a 
s P'ne-shaped squame at the first joint of the peduncle : anterior pair 
°J kgs didactyle. 
* Eyes sub globose, not thicker than their peduncles. 
The coxce of the third pair of legs of the female, of the fifth pair 
01 Ihe male, perforated. These perforations are for Ihe passage of 
t ne semen and of the eggs ; and although placed differently in other 
§ e nera, yet they serve the same functions. 
Abd *^ enus 2f5 - ASTACUS. Leach's MSS. 
° me n with Lhe sides of its segments obtuse : middle tail lamella com- 
S, 
P°sed of 
one piece. 
' A A st. Gammarus. Rostrum on each side with four teeth, and with 
^ °n each side of its base. 
c er Gammarus. Linn. Syst. Nat. i. 1050. Astacus Gammarus. Penn, 
j’k. Zoo/, iv. 9. pi. lo. Astacus marine s. Fair, Sapp. Ent. Syst. 406. 
•air. Gen. Crust, et Insect, i. 51. Astacus Gammarus. I. each, Ed in. En- 
r ‘icl. vii, 398 . — Trans. Linn. Soc. xi. 344. — Sapp, lo Encycl. lirit. i. 420. 
This species, which isthecommon lobster of our markets, inhabits 
deep clear water at the foot, of rocks which hang over the sea. They 
^eed during the early summer months, and are very prolific, Baxter 
Uving counted no less than 12,444 eggs under the abdomen. In 
)'arm weather they are very active; they have the power of spring- 
n g backward in the water to a most astonishing distance into their 
0 ®sin the rocks, as has been frequently observed by naturalists of 
,. d- Their food consists of dead animal matter, and, it is said, also 
sea-weed. The female is stated to deposit her eggs in the sand, but 
the 
young state is not known 
The common lobster inhabits the European ocean. It is found in 
^ <r > great abundance in the North of Scotland; but is much more 
jmunon on the coast of Norway, from whence the London markets 
le ° r the most part supplied. > 
Aid GenUS - 27 • POTAMOBIUS. Leach's MSS. 
"men with the sides of its segments sharp : middle tail lamella bi- 
a 
Partite. 
* ’ l " P rt.flu-ointilis . Rostrum laterally dentated, the base with one 
Cuu° th ° n 6aCh side ‘ 
Cci Astacus. Linn. Syst. Nat. 1. 1051. Astacus astacus. Penn. 
