240 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



The tentacles contain two, a proximal and a distal, very narrow and delicate 

 lines of spicules, which run to the end of the basal half or two-thirds. In a lateral 

 view of the pinnule these appear as a closely set row of very narrow triangles with 

 open distal apices. 



Heterometra quindupUcava. — Each ambulacral lappet usually contains one or 

 two extremely slender spicules, which usually extend, at right angles to the pin- 

 nulars, to near the sacculi ; but there may be a branched spicule, or a net of one or 

 two meshes. 



The tentacles contain a continuous line of extremely slender spicules. 



BeteroTiietra hengaleiisis (fig. 796, p. 372). — Each ambulacral lappet contains a 

 small spicule, which is Z-shaped, forked, multiradiate, or containing one or two 

 meshes; if elongated, the elongation is parallel to the edge of the pinnulars; be- 

 tween each of these and the pinnulars there is us>ially a slender, straight spicule, 

 at right angles to the pinnulars. 



In their proximal half the tentacles contain two slender, continuous lines of 

 spicules, one along the distal, the other along the proximal border. 



Heterometra compta, — Near their tips the ambulacral lappets contain very 

 minute calcareous reticulations of one, two, or three meshes. The perisome between 

 the sacculi and the pinnules is unplated. 



The tentacles contain two narrow lines of spicules, one distal and one proximal, 

 which extend to about the end of their proximal half. 



Heterometra pulchra. — The tips of the ambulacral la]>pets contain minute 

 forked, branched, or multiradiate spicules. Beneath these are long, more or less 

 irregular spicules, usually one over each sacculus. These lie at right angles to the 

 pinnulars, and are sometimes forked or paired, or gathered into small groups. 



There appear to be no spicules in the tentacles. 



Heterometra reynaudii. — Near their tips the ambulacral lappets contain small 

 spicules, which may be straight and parallel to the pinnulars, forked, or multi- 

 radiate. There are no deposits between the sacculi and the pinnulars. 



Each tentacle contains a distal and a proximal fine continuous line of spicules, 

 which runs for about half of its length. 



Heterometra quindupUcava. — Near their tips the ambulacral lappets usually 

 contain forked or branched spicules, which lie parallel with the pinnulars; some- 

 times these spicules are multiradiate, and sometimes they form one or two meshes ; 

 occasionally the lappets contain several long spicules lying at various angles. 

 There may be other elongate spicules between these and the row of sacculi. 



The tentacles contain two conspicuous fine lines of spicules, a distal and a 

 proximal, which run for about half their length. 



Hovmlometra denticulata. — Each ambulacral lappet contains a very slender 

 branched, triradiate or quadriradiate spicule lying parallel to the edge of the pin- 

 ntdars ; below this is a long straight spicule reaching nearly to the border of the 

 pinnulars ; in addition to the latter the lateral perisome of the pinnules contains a 

 series of long spicules, the majority of which lie at right angles to the edge of the 



