430 PROCEEDINGS OF THE NATIONAL MUSEUM vol.89 



of the smaller plates may bear one to five shorter and slenderer spines, 

 and a few may bear as many as 15 spines. Going out along the arms 

 the number of spines in the paxillae gradually decreases until, near 

 the arm tips, the paxillae bear only one to three spines, and still 

 further out only one or two. 



Crossaster squamatus is probably only an extreme form of the 

 widespread and very variable C. 'papposu^^ in spite of the fact that 

 its general appearance is very different. 



LEPTASTERIAS (HEXASTERIAS) BARTLETTI, new species 



Plate 59 



Description. — Arms 6; R=25 mm.; r= 8 mm. The abactinal skele- 

 ton is irregularly and evenly reticulate with no indication of a carina! 

 series of plates, the papular areas small and often containing small, 

 isolated, rounded plates. The area occupied by the plates is of about 

 the same size as, or perhaps greater than, that occupied by the papular 

 areas. Just above the row of superomarginals there is a regular row 

 of rather large papular areas (the supramarginal groove) resembling 

 those in the row between the superomarginals and inferomarginals 

 (the intermarginal groove). A row of actinal plates, which at first 

 are as large as the inferomarginals but rapidly decrease in size, extends 

 to about the middle of the arm. 



The abactinal spinelets are numerous, one to five or even six (usually 

 one, two, or three) to a plate. They are small and short, two to four 

 (usually about three) times as long as broad, cylindrical with round- 

 edly truncate, spinous, and often striate, tips. The variation in length 

 and slenderness is relatively slight so that the entire aboral surface 

 presents a uniform covering of fine short spines. 



The superomarginal spines are somewhat longer and stouter than 

 the abactinal spines, though of the same character. There is usually 

 one to a plate, though sometimes in the middle of the arm this is 

 accompanied by one or even two smaller and slenderer ones. The 

 inferomarginals bear spines resembling those of the superomarginals 

 though slightly larger and stouter and slightly curved distally. There 

 is usually one to a plate, but in the middle of the arm often two are 

 present. There is a row of 9-11 actinal spines, one on each plate. 

 These at first resemble the spines on the inferomarginals but outwardly 

 decrease in size and disappear at about the middle of the arm. 



The adambulacral plates each bear two spines, which are slenderer 

 than those on the inferomarginals, though of about the same length; 

 the inner spine, at the furrow edge, is slenderer and slightly longer 

 than the outer. The pairs of spines on successive plates are alternately 

 nearer to and farther away from the furrow. 



