76 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



Inferomarginals not extending laterally beyond superomarginals. 

 Lateral spines 2, tapering and sharp, situated at outer end of 

 plate, the upper the longer and equal to a little over 2 plates in 

 length. Sometimes a third very much smaller spine is added at the 

 inner end of series but is not constant. Spaced from the lateral 

 spines, near inner end of plate and aboral margin is a smaller, 

 sharp, flattened appressed spine a little longer than its plate; at the 

 base of ray there are usually 1 to 3 additional similar spines 

 forming a series continuous with the lateral spines. If the number 

 of lateral spines is represented by Roman numerals and the acces- 

 sory actinal marginals by Arabic, the spine formula for the first 

 inferomarginal of type is 0+4 or 5 or I-|-4 or 5; for the second, 

 II+3 or 4; for the third II+2, 3, or 4; for the fourth, II+2, 3, or 4: 

 from here it is II+2 usually or in those specimens in which the 

 third small lateral is not developed, Il-fl. The inner actinal spinulo 

 usually disappears on the outer third of ray, while the accessory or 

 third lateral persists, if it happens to be present at the base of 

 ray. The spine formula for the outer third of ray is commonly 

 II+l, or II+O. The general surface of plates is armed with spaced 

 lanceolate sharp, or exceptionally, blunt flattened spinelets directed 

 outward, 2 to 4 being enlarged and forming a series adorally to 

 the lateral spines. These sharp spinules were not reckoned in the 

 above formulas, as they stand entirely out of line of the transverse 

 series. 



Terminal plate rather small, about as wide as long with a notch 

 at both distal and proximal ends, between which runs a shallow 

 sulcus. 



Adambulacral armature: (1) A furrow series of 3, the middle the 

 longest, curved, compressed but slender, with sharp edge toward fur- 

 row, the laterals a little shorter only slightly flattened, slenderer, 

 tapering, and pointed. (2) On the actinal surface, a longitudinal 

 series of 3, the median about as long as the middle furrow spine, flat- 

 tened and sharply or bluntly pointed, the laterals much slenderer, 

 and about two-thirds as long as the median. Sometimes only 2 

 stand in this series. Back of these, 3 or 4 much shorter and slenderer 

 spinules form a series or group. A large specimen (locality uncer- 

 tain) has all the subambulacrals flattened and round tipned, the en- 

 larged spine being spatulate. The first adambulacral is much com- 

 pressed and bears 2 transverse contiguous rows of numerous slender 

 spinules, and has no enlarged subambulacral, but the second plate, 

 although compressed somewhat, bears an enlarged spine. 



Mouth plates narrow and small, each traversed by 2 parallel series 

 of spines ; the marginal Avith about 15, small slender spines or spin- 

 ules, similar to those of the first adambulacral, the inner 2, abruptly 

 enlarged, flattened, and round tipped. The superficial spinules are 



