32 



OUTLINES OF NATURAL HISTORY. 



The fifteenth segment (being the first of the abdomen) 

 carries (in the males) a pair of singular grooved processes(/0, 

 and the sixteenth, seventeenth, eighteenth, nineteenth, oxiditiven- 

 tieth segments carry each a pair of appendages which are 

 known as " swimmerets" (i,j, I; I, m), and each of which 

 consists of an undivided base, terminated by two flattened 

 paddles or oars (fig. 13, 2). The last of these pairs of swim- 

 merets (m) has the terminal paddles greatly expanded. 



The twentij-first segment {t) carries no appendages, and 

 is simply placed between the expanded swimmerets of the 

 twentieth ring, thus constituting a most powerful tail-fin, 

 by the strokes of which the animal can propel itself through 

 the water, tail foremost, for an astonishing distance, and 

 with great rapidity. 



The following table shows the segments of which the 

 Lobster is composed, with their proper appendages : — 



Head, 



Thorax, 



Abdomen, 



1st, Eyes. 



2d, Lesser antennae. 



3d, Greater antennae. 

 4th, Pair of biting-jaws. 

 5tli, First pair of chewing-jaws. 

 6tli, Second ])air of chewing-jaws. 

 ■ 7th, First pair of foot-jaws. 



8th, Second pair of foot -jaws. 



9th, Third pair of foot-jaws, 

 loth, First pair of legs (great claws), 

 nth, Second pair of legs (small claws). 

 1 2th, Third pair of legs (small claws). 

 13th, Fourth pair of legs (pointed). 

 ,14th, Fifth pair of legs (pointed). 



''15th, Grooved appendages. 

 1 6th, Small swimmerets. 

 i>th, ,, ,, 



i8th, ,, „ 



19th, ,, ,, 



20th, Large swimmerets. 

 2 1st, No appendages. 



We may add to this description of the Lobster, that not 

 only is the body composed of a succession of segments, 

 some of which are movably jointed to one another, but 

 the limbs are also composed of distinct pieces or joints, 



