290 



BULLETIN 54, UNITED STATES NATIONAL MUSEUM. 



EXOSPH/EROMA RHOMBURUM (Richardson). 



Sphieromn rhoinburuin Richardson, Proc. U. S. Nat. Mus., XXI, 1899, pp. 835-836; 

 Ann. Mag. Nat. Hist. (7), IV, 1899, p. 179; American Naturalist, XXXIV, 

 1900, p. 222. 



Locality. — Monterey Bay, California. 

 Surface of body punctate; color, whitish yellow. 

 Head small. First pair of antennse reach almost to the posterior 

 margin of the tirst thoracic segment. Second pair of antenna? extend 

 quite to the posterior margin of the tirst thoracic segment. Eyes sit- 

 uated post-laterally. 



Thoracic segments equal in length. Epimera l)road and short, 

 extending downward, forming an angle with the 

 segments. 



First abdominal segment as long as any of the 

 thoracic segments, crossed by suture lines and 

 surmounted by two tuber- 

 cles, close together, one on 

 either side of the median line. 

 Terminal segment with its 

 extremity produced in a 

 process rhomboid in shape, 

 and with sides infolded, forming a kind of fun- 

 nel-like opening when seen from beneath. At 

 the base of this segment are two tubercles, 

 which are continuous with two longitudinal 

 ridges in the center of the segment. These 

 ridges unite near the extremity, and continue as 

 one median ridge. The uropoda are siiorter than 

 the terminal segment; the outer branch is more 

 lanceolate in shape; l)oth are of equal length. 



Two specimens were taken at Monterey Bay, California, by Mr. 

 Heath. 



rype.—OAi. No. 22.578, U.S.N.M. 



This species is similar to S. {'.) egreghDii- Chilton, from Akaroa, but 

 diti'ers in the presence of two tubercles on the tirst abdominal segment, 

 in the presence of two tubercles and two longitudinal ridges imiting 

 in a single ridge on the terminal segment, and in the equality in length 

 of the two branches of the uropoda. 



Fig. 303.— EXOSPH.ER0MA 



RHOMBURUM. ABDO" 

 MEN. X Vi\. 



Pig. 304.— E X OS p h jv. r oma 



RHOMBURUM. MAXILLI- 

 PED. X 511. 



