THE AMERICAN LOBSTER. 



DESCRIPTION. 



The lobster {Homarxis amcricanus) belongs to that group of the Crus- 

 tacea called the Decapotla, because all of its uiembers are provided with 

 ten feet, more or less adapted for walking-. To the Decapoda also belong 

 the crabs and the shrimi)s, jjrawns, and crayfish. The crabs are less 

 related to the lobster than the other forms mentioned, and may be 

 readily distinguished from them by the relatively great breadth of the 

 body and the small size of the abdomen or tail, which is doubled under 

 the thorax to form the " apron." The lobsters, crayfish, shrimps, etc., 

 are elongate forms with the tail or abdomen very large and extended 

 more or less in the same horizontal plane with the anterior part of the 

 body. The lobster and the crayfishes are somewhat closely related, but 

 difler, among other characters, in the number and structure of the gills 

 and in the relative size of the flat plate or scale which is attached at 

 the base of the antennae or long feelers. The Pacific Coast crayfishes 

 have 18 gills, those east of the Eocky Mountains have 17, while the 

 lobster has 20. The appendage of the antenna is large in the cray- 

 fishes, but very small in the lobster. Moreover, the crayfishes rarely 

 exceed 5 or 6 inches in length, while the adult lobster is much larger, 

 as seen in the markets, seldom measuring less than 9 or 10 inches. 

 The spiny lobster, the "lobster" of the Pacific Coast, is readily distin- 

 guished from the crayfish and the common lobster by the total absence 

 of great claws, by the greater length and stoutness of the antenniie, and 

 by the presence of large, broad-based, si)inous processes on the back. 



The body of the lobster is divided into two distinct regions, the 

 cephalothorax and abdomen. The former consists of the head and 

 thorax fused into one united whole. That portion which would consti- 

 tute the head, were it separate, bears the eyes, the two pairs of feelers, 

 and the mouth, with the several pairs of modified limbs which surround 

 that organ and aid in tearing up the food and passing it between the 

 lil)S. The thoracic portion of the cephalothorax is furnished with five 

 pairs of stout limbs, the first pair bearing the great claws, which are 

 rarely of the same size on the two sides, and the last four pairs being used 

 in walking. From the fact that this portion of the body bears five pairs 

 of appendages, it is assumed that it represents five fused segments. 



The abdomen is narrower than the cephalothorax and is composed 

 of six separate segments movable on one another. In the female the 



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