306 



BULLETIN 93, UNITED STATES NATIONAL MUSEUM. 



Cirrus vi has rami of 15 segments, most of them bearing five pairs 

 of spines (fig. 86a). 



FIG. 86. CHTHAMALUS STELLATUS ANGUSTITERGUM, ABACO. a, INTERMEDIATE SEGMENT 



OF CIRRUS VI. 6, LABRDM. 



This is the race of the Bahamas and Florida Keys. It is probably 

 a species distinct from Ch. stellatits. 



CHTHAMALUS STELLATUS BISINUATUS, new subspecies. 



Plate 71, figs. 6, 60. 



Type. Cat. No. 48085, U.S.N.M., from Santa Catharina Island, 

 Brazil. 



Articular ridge of the scutum prominent in the middle, hollowed 

 out above and abruptly terminated below; the articulating margin 

 therefore being bisinuate. Pit for the adductor muscle is deeply 

 excavated, as in typical stellatus, and there is no adductor ridge. 



The tergum is wider than in C. s. angmtitergiim. The scuta 1 

 margin of the articular ridge is prominent. There is a small spur, 

 as in angustitergum. The crests for the depressor muscle are strong 

 and long, and there is a deep fissure or furrow next to the lower crest, 

 running far up the central part of the valve. This furrow is present 

 in both of the specimens I examined, and has not been found in any 

 other species. Whether it is a constant character of this race re- 

 mains to be determined. 



The dingy, corroded wall measures about 7.5 mm. in diameter. 



Darwin has given some notes on specimens from Gorriti Island, 

 Uruguay, probably belonging to this race. 



The specimens in the United States National Museum are from 

 Brazil; Rio de Janeiro, collector unknown, and Santa Catharina 

 Island, Isaac Lea collection. Both lots are preserved dry. 



