140 BULLETIN 54, UNITED STATES NATIONAL MUSEUM. 



groove. The first pair of antenna* have the first two articles almost 

 confluent and scarcely distinguishable; the lirst is twice as long as the 

 second; the third is also twice as long as the second. The flagellum is 

 composed of eleven articles. The first pair of antennae extend almost 

 to the middle of the last article of the peduncle of the second pair of 

 antennae. The second pair of antennae have the first two articles short, 

 the second a little shorter than the first; the third is nearly twice as 

 long as the second; the fourth and fifth are suhequal and each twice as 

 long as the third. The flagellum is composed of sixteen articles. The 

 second antennae extend to the posterior margin of the second thoracic 

 segment. The maxilliped is composed of seven articles. The palp of 

 the mandibles is composed of three articles. The frontal lamina is 

 longer than wide, and has the anterior margin produced in a long, 

 narrow acute median process. 



The first segment of the thorax is slightly longer than any of the 

 others, and has two small inconspicuous tubercles on the anterior por- 



a b c d 



FIG. 120. EXOCORALLANA TRICORXIS. a, MANDIBLE. X 61|. 6, MAXILLIPED. X 51|. C, FIRST 



MAXILLA, x 51 1. d, FRONTAL LAMINA, x 51|. 



tion, one on either side of the median line. The epimera are distinct 

 on all the segments with the exception of the first. They are all 

 crossed obliquely by an arched carina. The outer post-lateral angles 

 of the first two are rounded. In the last four the outer post-lateral 

 angle is produced beyond the posterior margin of the segments. 



All the segments of the abdomen are distinct. The second and third 

 segments have the posterior margins tuberculate; the fourth segment 

 has two transverse rows of tubercles; the fifth segment has three 

 transverse rows of tubercles. In the fourth and fifth segments there 

 is a narrow median depression, this area having only a single longi- 

 tudinal row of tubercles right in the median line, two for each of the 

 segments. The sixth or terminal segment is triangulate in shape 

 with the apex rounded and furnished with short spines. At the base 

 is a transverse row of tubercles ' on either side of a shallow median 

 longitudinal groove or furrow. Below the row of tubercles and on 

 either side of this median groove the lateral portions of the segment 



