248 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



Along the sides of the pinnules, near the pinnulars, there is usually a con- 

 tinuous band of the squarish plates, about three to eacli pinnular, the distal outer 

 corners of which are broadly cut away by the sacculi. Sometimes these are 

 reduced to triangular plates with their outer apices between the sacculi, or to very 

 small, rounded plates between the sacculi. When the covering plates are well 

 developed they may resemble them, but they are somewhat larger, with a very 

 irregular outline, and usually slightly higher than broad. 



The perisome over the genital glands is covered with a continuous layer of 

 large and delicate, more or less irregular plates. 



There are no spicules in the tentacles. 



Tropiometra picta. Toward the distal ends of the outer pinnules there is in 

 the outer portion of each ambulacral lappet a short median rod, which may be 

 forked, or a minute irregular plate of one or two meshes. A second small speci- 

 men showed similar deposits. 



There are no plates or spicules in the lateral perisome of the pinnules. 



There appear to be no spicules in the tentacles. 



Tropiometra indica. Each ambulacral lappet contains a usually straight or 

 very slightly curved, rarely forked, rod with roughened ends, which lies at right 

 angles to the pinnulars. 



Other than these, the perisome of the pinnules contains no deposits. 



Spicules are extremely rare or altogether absent in the tentacles. 



Family CALOMETRIDJE. 



Neometra alecto (figs. 835-837, p. 405). Along the sides of the pinnules and 

 immediately adjoining the pinnulars is a continuous row of side plates, from five 

 to seven to each pinnular. 



These are of very peculiar and characteristic shape. The base of each slightly 

 overlaps the base of the one distal to it. On the distal side, just beyond the base, 

 there is a deep semicircular excavation reaching inward for about one-third the 

 length of the plate as measured along the base. On the proximal side there is a 

 similar but shallower excavation. Between these excavations the plate is reduced 

 to about half the basal length. When the plates are in their normal position the 

 excavations of adjacent plates together form circular holes through which the 

 distal third or half of the sacculi protrude. The distal lateral excavation is 

 bordered outwardly by a narrow arm rounded distally, which, making a slight 

 angle with the pinnular, reaches a point almost but not quite directly over the 

 distal end of the base where it adjoins the succeeding plate. Beyond this narrow 

 arm limiting the distal excavation outwardly the plate leans proximally at an 

 angle of about 45, so that the outer portion beyond the lateral excavations may 

 be said to consist of a narrow distal arm over the deep distal excavation, making 

 an angle of usually less than 45 with the base, and a very much broader proximal 

 portion, making an angle with the base of about 45. This latter terminates in 

 a straight line perpendicular to the pinnular directly over the proximal end of 

 the base where it adjoins the narrow distal extension of the plate just proximal 



