1SOPODS OF NORTH AMERICA. 



357 



FIG. 384. IDOTHEA GRACILLIMA. X 5. 



filiform, the thoracic segments subquadrate, head quadrate. He refers 

 to the linear post-abdomen, which is truncated at the apex, three- 

 jointed, and marked on either side with a suture. The antennae are 

 described as being a little shorter than 

 half the body, with a ten- to twelve- 

 jointed flagellum. 



A species of Idothea was sent to the 

 U. S. National Museum by Doctor Rit- 

 ter. The specimens, which are eight in 

 number, were collected by him at Boli- 

 nas, California. They are more closely 

 allied to /. gracillima than to any other 

 known species of Idotlma from the Pacific 

 coast of North America. Until evidence 

 can be given of their distinctness, 1 shall 

 consider them identical with I. gracil- 

 lima (Dana). 



Body slender, about seven times 

 longer than wide/' with the sides nearly 

 parallel. Surface entirely smooth. 

 Color in alcohol uniformly pinkish. A 

 note referring to the color of the specimens in life says that they are 

 green, brown, and striped. 



Head quadrate, with rounded antero-lateral margins, and a slight 

 median excavation in the anterior margin. Eyes situated at the 

 extreme lateral edge and about the middle of the head; they are small 



but distinct. The first pair of 

 antennae are four-jointed, and ex- 

 tend a little beyond the extremity 

 of the second peduncular joint of 

 the second pair of antennae. The 

 second pair of antennae are equal 

 to half the length of the body; 

 the last two joints of the pedun- 

 cle are subequal; in the smal lei- 

 specimens the flagellum is com- 

 posed of ten joints; in the larger 

 ones there are eighteen joints. 



The first thoracic segment is short in the middle but is produced 

 antero-late rally on either side; it is not wider than the head. The 

 second, third, and fourth segments are subequal in length and are 

 longer than the first segment. The fifth, sixth, and seventh segments 

 gradually decrease in length. The epimera of all the segments are 

 extremely narrow; those of the second and third segments extend but 

 half the length of the segment; those of the fourth and fifth segments 



The female is figured. The body is somewhat broader than in the male. 



FIG. 385. IDOTHEA GRACILLIMA. ABDOMEN, SHOW- 

 ING VARIATIONS IN FORM. 



