CiENOPEDINA PULCHELLA. 223 



Caenopedina pulchella, comb. nov. 



Hemipedina pulchella A. Agassiz and Clark, 1907. Bull. M. C. Z., L, p. 245. 



Plates 91, figs. 18-22; 103, figs. 1-3; 105, figs. 6, 7. 



In superficial appearance this species is so unlike any other member of the 

 genus that its real relationship was not suspected until the abactinal system was 

 examined, and it was only by the inspection of the tubercles that its generic 

 position was determined. The larger specimen is 14 mm. in diameter, while the 

 height of the test, the diameter of the abactinal system and that of the actino- 

 stome, are each about half as much. In the smaller specimen, which is only 

 about half as large the proportions do not seem to be essentially different, though, 

 as might be expected, the abactinal system and actinostome are perhaps a little 

 larger relatively. But while the smaller specimen has 6 interambulacral and 7 

 ambulacral plates in each column, the larger has 8 and 11 respectively. The 

 genital plates (PI. 103, fig. 1) are large, heptagonal and broadly in contact with 

 each other. The central part of each plate is rough, one might almost say 

 sculptured, and on the proximal portion are two or three secondary tubercles. 

 The pore is near the centre. The ocular plates are small, scarcely one fifth as 

 large as the genitals; like the latter, their surface is rough but they carry no 

 tubercles. The periproct is small, not so large as a genital, and is covered b}' 

 about 20 rather large plates, none of which however carry tubercles. 



The interambulacral plates are high, but those above the ambitus are each 

 almost completely covered by the primary tubercle; there is just room at the 

 corner of each plate for a small secondary tubercle. Actinally the primary 

 tubercles are much smaller and there is room, on both the outer and inner sides, 

 for some small secondary tubercles; miliary tubercles seem to be wanting. 

 Excepting one or two of the uppermost in each column, the ambulacral plates 

 each carry a primary tubercle; those at the ambitus are largest but e\'en they are 

 little larger than the actinal interambulacral tubercles. Aside from the primaries 

 only a very few tubercles and those, small actinal secondaries, are found in the 

 ambulacra. The pore-pairs are small, forming a narrow almost vertical area. 

 The ambulacra are about three fourths as wide as the interambulacra at the 

 ambitus. 



Aside from the primordial ambulacral plates, the buccal membrane (PI. 103, 

 fig. 2) is almost naked, only a very few, small, rounded, non-ambulacra! plates 

 being scattered here and there. There are pedicellariae and a few small spines on 



