MARETIA TDBERCULATA. 247 



in the photographs (PI. 160, figs. 5-7). The petals are narrow and the pore- 

 pairs are small, so these points do not show well in the figures. Petals I and 

 V are about 9 mm. long and have 17-19 pore-pairs in each series of which the 

 basal 5 or 6 can scarcely be detected with a lens; these petals are only 2 mm. 

 wide and the interporiferous area is greatly reduced; the tip of the petal is quite 

 pointed. Petals II and IV are only 6 mm. long and 1.5 mm. wide; the pore- 

 pairs of the basal half dozen plates cannot be made out but there are 9 evident 

 pore-pairs in the posterior series and 6 slightly smaller ones in the anterior 

 series. Ambulacrum III is flush with the adjoining interambulacra and is not 

 differentiated in any way, save that there is on each side a series of small primary 

 tubercles. The apical system is very compact and there are no genital pores. 

 The posterior end of the test is vertical with the small nearly circular periproct 

 near its upper margin. The subanal fasciole is narrow but distinct and encloses 

 a very complex subanal plastron, nearly vertical in position and markedly 

 convex; on each side are included no fewer than 7 ambulacral plates of which 

 the lowest (the sixth from the peristome) is much the largest and the two upper- 

 most are smallest and barely come within the fasciole; all but the lowest and 

 uppermost are accompanied by large tube-feet so that there are 5 of these on 

 each side; the entire plastron is about 9 mm. wide by 4 mm. high. The sternum 

 is about 8 mm. long but only the posterior three eighths is occupied by tubercles. 

 The labrum is nearly 5 mm. long by 1 mm. wide and reaches almost to the third 

 ambulacral plate on each side. The peristome is about 4 mm. wide by 2.5 mm. 

 long and is scarcely sunken at all. The specimen was fairly well covered with 

 spines and the general color was very light purplish gray, which with the passage 

 of time has become a very light brown; the larger spines are nearly white. 



The miliary spines are minute and slightly thickened at the tip while the 

 secondaries are conspicuously larger and are more or less curved; on the lower, 

 posterior parts of the test, they pass into the ventral primaries which arc 8 mm. 

 long, at the longest. The large dorsal primaries are 10-12 mm. long and are 

 slightly curved. Pedicellariae are not abundant, but three kinds were found. 

 The ophicephalous are common on the ventral ambulacra; the valves are only 

 .14-.16 mm. long besides a loop of .06-.09 mm., and there is nothing character- 

 istic in their form. The rostrate or coarse tridentate are not common; they 

 are similar to those of Gonimaretia laevis but the valves are rather more pointed; 

 they measure .27-.43 mm. in length. The triphyllous are also uncommon and 

 the valves scarcely exceed .10 mm. in length. 



The absence of genital pores and the appearance of the petals show at 

 once that this is a young individual. The large primary tubercles of the dorsal 



