380 



BULLETIN 54, UNITED STATES NATIONAL MUSEUM. 



Fig. 414. — Syntdotea erosa 

 (After Benedict), x 2. 



Head wider than long, 2^ mm. :5 mm., with the anterior margin 

 deeply excavate between theantero-lateral angles. The eyes are small, 

 round, composite, and situated on either side, some distance from the 



lateral margin, which is expanded to form 

 a narrow border. Two prominent tuber- 

 cles, one on either side of the median line 

 are placed just behind the anterior margin, 

 from which position they overhang the 

 frontal notch. Just in front of each eye is 

 a low tubercle almost inconspicuous. Be- 

 tween the eyes, one on either side of the 

 median line, are two large but low eleva- 

 tions. Back of these elevations is a low 

 ridge. The first pair of antenna? have the 

 first two articles short and subequal; the 

 last two are subequal, and each is one and 

 a half times longer than either of the two 

 preceding articles. The first pair of an- 

 tenna? extend to the middle of the fourth 

 article of the peduncle of the second pair of 

 antenna?. The first two articles of the sec- 

 ond pair of antenna? are short and subequal ; the third and fourth are sub- 

 equal and each is about twice as long as either of the two preceding 

 articles; the fifth is one and a half times longer than the fourth. The 

 flagellum is composed of seventeen articles. The 

 maxillipeds have a palp of three articles. 



The second, third, and fourth segments of the tho- 

 rax are subequal and are the longest, each being 

 about i mm. longer than any of the other segments, 

 which are nearly subequal, the seventh being a little 

 shorter than the sixth. The epimera of all the seg- 

 ments are firmly united with the segments, and there 

 is no indication of a separation. On each segment 

 of the thorax, on either .side of the median line and 

 a short distance from the lateral margin, is a low 

 elevation, which in the first segment at its anterior 

 portion is produced into two low tubercles. 



The abdomen is composed of a single segment, which has a suture 

 line at its base on either side; it is Ti mm. long, about one-third the 

 entire length of the body, and is 5 mm. wide. It tapers to a rounded 

 extremity, which has a small and shallow median excavation, almost 

 inconspicuous. 



All the lepfs are similar in structure. 



Fu;. 415.— Synidotea 



EROSA. MAXILLIPED. 



X 15i. 



