266 Description of a Species of Caligus. 



Fig. 3. A female, natural size. 



Fig. 4. a. View of the rudimentary or second pair of legs, or maxillipeds ; t», 

 termination of third pair. 



Fig. 5. a. Ventral muscle, exhibiting its subdivision between the sternums of 

 the two pairs of natatory legs ; b, a second subdivision in the same muscle, below 

 the posterior of the above sternums. 



Fig. 6. a and b. View of the posterior thoracic joint, (see fig. 7,) with the valves 

 in the circulation ; the two lateral valves on the back and the central on the venter. 



Plate IV. 



Fig. 7. Back view of a male, with the muscles seen in this view. Those mark- 

 ed with capital letters, move the segments of the body ; those with small letters, 

 move the several organs below. F, the posterior thoracic segment ; G, the anterior 

 abdominal; H, the posterior abdominal. 



Fig. 8. A portion of the shell about the eyes, shewing the areolets exhibited by 

 it; the dotted line marks the limits of the dark ground on which the eyes are sit- 

 uated, and the dotted circles the eyes themselves. 



Fig. 9. Alimentary canal, exhibiting the esophagus, the stomach and the intes- 

 tine, with its glands, and the muscles of the rectum. The mouth at the upper ex- 

 tremity is represented as turned back, so as to show its under surface. 



Fig. 10. Anterior extremity of the esophagus. 



Fig. 11. A portion of the intestine. 



Fig. 12. View of the buccal mass, in its natural position. Between the line a a, 

 and a b a, is the opening to the mouth, d, the outer extremity of the mandibles, 

 with the tendon and its muscles attached. 



Fig. 13. The same with a portion of the upper membrane and the mandibles re- 

 moved. 



Fig. 14. The mandibles, together with some of the organs adjacent to their in- 

 ner extremities, showing their relative position. 



Fig. 15. The upper lips, with its two pairs of muscles. 



Fig. 16. The same, with the extremity retracted by the inner pair of muscles. 



Fig. 17. Under view of the buccal mass, with the esophagus attached, h h are 

 processes lying in the teguments of the body, with which the buccal mass forms an 

 articulation at their anterior extremity, g the processes in which the elevators of 

 the buccal mass are inserted. 



Plate V. 



Fig. 18. Under view of female, exhibiting the nervous system, and the ovaries, 

 and ovarian tubes. Fig. 18, a, the first pair of maxillipeds in the female ; 18, b, the 

 fourth pair in the same. 



Fig. 19. A view of the cup and an antenna, together with a portion of the lat- 

 eral margin of the animal, exhibiting its spines. The dotted lines in the antenna 

 represent the nerve with which this organ is largely supplied. 



Fig. 20. The cephalic and thoracic ganglions, exhibiting their close union, and 

 the nerves they give out ; the outlined organ in front, represents the eyes, attached 

 to the ophthalmic nerves. 



Fig. 21. Genital system in the male. 



Fig. 22. Part of the abdomen of a female with an appendage to the same. 



Figs. 23, 24, 25. Illustrate some facts connected with the change of skin. 



