74 BULLETIN 76, UNITED STATES NATIONAL MUSEUM. 



passing gradually into the lateral face of ray. The dorsolateral margin, on the 

 other hand, is very abrupt. Plates arc covered with s(|uamiform, broadly lanceo- 

 late, ovate, obovate, blunt, or often sharp spinelets, which increase in size toward 

 lower end of plate, but are very slender and terete in the fasciolar grooves. About 

 1 mm. from the upper end of each plate is a flattened slender tapering spine, attaining 

 a length of 3.5 mm., the series of which extends the length of the ray, being absent 

 occasionally from the first one to three plates. These spines or spinules either 

 stand out from side of ray or are frequently appressed against it and may be 

 equal to or longer than superomarginal spinules. Spaced from the above spinule, 

 about midway between its base and lower end of plate, is a second similar but 

 shorter spinule, forming on the plate a vertical series, and a longitudinal series 

 for about two-thirds the length of ray. Some specimens have a few plates with 

 three spinelets in a vertical series. All the spinelets covering the marginal plates 

 are sheathed by membrane, which in alcoholic specimens causes these spinelets to 

 appear very com])actly placed, with broad rounded tips. Wlien the specimen is 

 dried the squamiform spinelets are seen to have narrower rough tips and to be 

 distinctly spaced. Terminal plate a trifle wider than long, rounded distally, con- 

 cave next to paxillar area, where three rows of pa-xillo" touch its free edge. The 

 granuliform covering is rubbed off. 



Adambulacral plates with a prominent angular margin to furrow. Armature 

 consisting of (1) furrow series of eight (seven in some specimens) delicate subequal, 

 membrane-invested, round-tipped spinelets, the two or three at either end of series 

 flattened with sides to furrow, while the four or two central spinelets have the edge 

 to furrow; the lateralmost spinelets are often shorter than the others; (2) on 

 the actinal surface are two or three longitudinal series of flattened, truncate or round- 

 tipped spinelets, four or five to each series. The outer spinelets are slightly wider 

 than the inner and all are subequal to furrow series. Actinal spinelets are sheathed 

 in a thick pulpy membrane which gives them a papilliform clavate appearance. 

 In dried specimens the spinelet is seen to be slenderer, but flattened, with a rounded 

 tip often wider than base. The first and second adambulacral plates are much 

 compressed, and each has two transverse series of spinelets, about twenty to twenty- 

 four on the first plate antl about sixteen on tlie second. 



Mouth plates elongated in the interradial direction, narrow, the median suture 

 being dilated near the middle. The spinelets are arranged in two parallel series 

 on each plate. The marginal series consists of about fifteen to eighteen short, 

 regular, slightly flattened spinelets, decreasing in length at outer end of plate, 

 but subetiual all along inner half. These spinelets stand close together and are 

 appressed against a superficial series of about the same number of heavier, c\din- 

 drical, subglobose or clavate skin-covered spinelets, which increase in thickness 

 toward the outer end of plate. The inner end of the combined pair of plates is 

 truncate, and either two or four spinelets at the angle are slightly larger and heavier 

 than the others, are slightly bent at base, and are appressed against innermost of 

 the superficial si)inelets. Tjqiically the spinelets are very regular in arrangement, 

 the superficial series of companion plates being close together in some examples, 

 in others separated bj- a conspicuous furrow. The armature of mouth plates is 



