242 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



Family MARIAMETRID^E. 



Pontiometra andersoni (fig. 798, p. 372) . In the lateral perisome of the pinnules 

 is a continuous row of conspicuous plates, trapezoidal in shape, with the angles 

 rounded, their distal sides being nearly half again as long as their proximal; a 

 thickened ridge traverses the plates diagonally from the produced distal outer to 

 the proximal inner angle; the distal border of each plate overlaps the proximal 

 border of the following. On some pinnules these plates are reduced to a row of 

 diagonally placed narrow triangles, which may be so narrowed as to almost re- 

 semble rods. Though forming a very conspicuous band, these plates are only of 

 moderate size, their height in lateral view being about one-third the diameter of 

 the pinnulars. 



Beyond the apex of each of these is a very minute plate of from 6 to 12 meshes, 

 which is elongated in a direction at right angles to the pinnulars. 



The perisome between the sacculi and the brachials is without deposits. 



No deposits were found in the tentacles. 



Oxymetra finschii. In one specimen, a cotype, no deposits were found in the 

 perisome of the pinnules. 



In another the lateral perisome of the pinnules contains a row of moderately 

 long straight spicules, one near each sacculus, extending outward and slightly 

 distalward from between the sacculi. 



In the first the tentacles were quite without deposits ; in the second there were 

 occasionally a few spicules along the distal side in the proximal portion. 



Oxymetra aranea. Near the tip of the lappets is a minute forked or branched 

 or multiradiate spicule, which may inclose a single cell ; between these and the row 

 of sacculi there may be single very slender straight spicules extending outward and 

 slightly distally in reference to the pinnulars. On many pinnules the perisome of 

 the pinnules appears to be quite without deposits. 



The perisome between the row of sacculi and the pinnulars is almost completely 

 covered by large irregular filmy plates. 



In about their proximal third the tentacles contain two very fine continuous 

 lines of spicules, a proximal and a distal. 



Dichrometra cttiata. Each ambulacral lappet contains two long straight or 

 slightly converging spicules, which extend downward nearly to the row of sacculi. 



Each tentacle contains, running along the distal side for about two-third of the 

 distance to the tip, a broad band of small matted spicules. 



Dichrometra ftagellata. There are no deposits in the perisome of the pinnules. 



There are no deposits in the tentacles. 



Dichrometra doderleini. Each of the ambulacral lappets contains a long 

 curved spicule, with the convexity distally, which runs near the distal border down 

 to near the row of sacculi. Rarely there may be one or two additional spicules 

 irregularly placed. 



Occasionally the tentacles contain a few very small spicules. 



Mariametra sulicarinata. The perisome of the pinnules contains a few widely 

 scattered irregular minute spicules. 



