244 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



There appear to be no spicules in the tentacles. 



Mariametra delicatissima. Each ambulacral lappet contains, running along its 

 distal border, a single very slender and slightly curved spicule, roughened at each 

 end, which extends downward almost to the line of sacculi, terminating just over the 

 spaces between them. Frequently these are much reduced, and sometimes they are 

 only evident as short rods. 



There are no deposits in the tentacles. 



Lamprometra palmata. There are no spicules in the perisome of the pinnules. 



On the distal side the tentacles may contain near the base one or two minute 

 spicules, or they may be quite without deposits. 



Lamprometra protectus. There are no deposits in the perisome of the pinnules. 



At the base the tentacles contain a conspicuous thin continuous row of spicules 

 both proximally and distally. 



Lamprometra gyges. Each of the ambulacral lappets contains a slender rod, 

 usually slightly curved, rarely branched, which extends downward to near the 

 sacculi, terminating above the spaces between them ; between the bases of these rods 

 there are commonly two other short rods, slightly curved away from each other, one 

 of which, proximal to the main rod, slightly overlaps its base, while the other is 

 directed distally and, making only a slight angle with the border of the pinnular, 

 passes beneath the main rod. 



Family COLOBOMETRID^E. 



Cenometra delicata. There appear to be no calcareous deposits in the perisome 

 of the pinnules. 



There are no deposits in the tentacles. 



Cenometra herdmani. There are no deposits in the perisome of the pinnules. 



There is a thin line of minute spicules along the distal side of the proximal 

 third of the tentacles. 



Cenometra unicornis. The perisome of the pinnules is naked, or contains 

 widely scattered and very minute spicules. 



The tentacles occasionally contain a few spicules on the distal side near the base. 



Cyllometra disciformis. Occasionally there are found in the lappets spicules 

 or straight rods which are almost perpendicular to the edges of the pinnulars, but 

 lean slightly distally; usually there are no deposits in the perisome of the pinnules. 



Along the proximal third or half of their distal side the tentacles contain a few 

 small irregular spicules, which usually do not form a continuous row. 



Cyllometra albopurpurea (figs. 776-778, p. 366). Each ambulacral lappet con- 

 tains an extremely fine, straight rod, reaching nearly to the line of sacculi, extending 

 outward and slightly distally in reference to the pinnulars. On some pinnules these 

 may be reduced to a minute spicule, or they may be altogether absent. 



Occasionally minute spicules may be found on the distal side of the base of 

 the tentacles. 



Decametra taprobanes. Each ambulacral lappet contains a single very slender 

 straight rod, which may be forked at the tip, directed outward and slightly distal- 



