268 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



Heliometra maxima. — Each ambulacral lappet contains a rather short, stout 

 rod, usually roughened at each end but commonly with the ends expanded and 

 pierced with from one to several holes. 



There are no deposits in the tentacles. 



Heliometra fflacialis. — In a specimen from Greenland each ambulacral lappet 

 contains in its outer portion a rod, usually straight but often with the inner end, 

 more rarely the outer also, broadened and pierced with one or two holes; some- 

 times the deposit takes the form of a very irregular and rudimentary plate with a 

 few holes of different sizes and shapes. 



Between and just outside of the saccuU are other deposits, rods, or extremely 

 irregular rudimentary plates, which are widely separated from each other; these 

 usually occur just below the ends of the rods in the outer ends of the lappets, one 

 or two beneath each rod. 



There are no deposits in the tentacles. 



In a specimen from the Western Bank the deposits are similar to those in the 

 preceding but somewhat more developed. The outer portion of the ambulacral 

 lappets usually contains an irregular elongated plate instead of a rod. 



There are irregular spicules occasionally to be found in the tentacles. 



In certain specimens from the Barents Sea, P. II. Carpenter found extensive 

 calcareous deposits in the perisome of the pinnules. 



Mortensen found a similar condition in others from eastern Greenland, in 

 which the plates along the pinnulars resemble those of Promachocnnus kerguelensis 

 or Anthovietra adriani, though they are not so well developed. He says that " the 

 covering plates are large, cribrous, of very irregular outline; the lower part is 

 much the larger and may consist of two separate plates lying very closely together; 

 they unite with the neighboring plates and thus form a complete covering on the 

 side of the ambulacral groove, interrupted only by the narrow spaces in which the 

 sacculi are lodged, sacculi and covering plates alternating regularly. The upper 

 part of the covering plate may be more or less separate, forming a very irregular 

 plate, whose adoral side is bent somewhat inward ; this part is much smaller than 

 the lower part, the plates being thus widely separated from each other. The con- 

 nection between the two parts may be repre.sented by a single rod, which forms, 

 however, mostly a more or less extensive network on its aboral, but not on its adoral, 

 side. On the genital pinnulae there are formed a number of thin, irregular plates 

 covering the widened portion between the joints and the ambulacral plates. When 

 dried these pinnulae thus show a very distinct irregular plating." He adds that the 

 perisomic plates are not found on the last six or seven pinnulars. 



Promachocnnus Jcerguelenms (fig. 807, p. 378).— Along the sides of the pin- 

 nulars is a continuous series of conspicuous plates, the distal border of each over- 

 lapping the base of the succeeding. The main portion of these plates is about as 

 high as broad, the distal and proximal edges being for the most part straight and 

 perpendicular to the base, but leaning somewhat distally in the terminal portion 

 of the pinnules. The outer angles are broadly rounded, and the middle half of 

 the outer border is produced into a roughly squarish process with an irregular 

 outer edge, which usually shows a narrow notch near the distal border. In the 



