ASTEROIDEA 139 



Description. The specimen measures R 55 mm., r 15 mm., br 17-18 mm. The disk 

 is sHghtly smaller, the interbrachial arcs less angular and the rays narrower than in the 

 drawing of the type. The compactness of the abactinal spinulation and spacing of 

 paxillae can best be appreciated from the enlarged photograph. Small abactinal plates 

 are scattered liberally among the larger; the former carry 1-5 spinelets, the latter 8-12, 

 with intergrades in the size and number of spinelets. This abactinal plating passes 

 without obvious change into that of the rounded sides of ray, and thence to actinal 

 surface where the spinelets are slightly longer and, interradially, the plates are arranged 

 in series from the furrow nearly to ambitus. These actinal plates or paxillae also form 

 4 longitudinal series adjacent to adambulacrals at base of ray, becoming less distinct and 

 reduced to about 2 series distally. The proximal plates of innermost actinal series carry 

 9 or 10 spinelets about as long as the outermost subambulacrals, and they gradually 

 decrease in length pari pasu with the latter all along the ray. On the outer third of ray the 

 plates of the adjacent longiseries (the inferomarginals) are larger, bearing 1 5-20 spine- 

 lets, and at very tip of ray touch the adambulacrals. Adorad to middle of R the in- 

 conspicuous inferomarginals, following the contour of the widening ray as in other 

 Perknasters, reach the interradius on the actinal face a short distance from the actual 

 margin. The plates become separated by the interpolation of secondary plates. One can 

 recognize the limits of the technical abactinal surface by the change from a wrinkled, 

 pustulated skin between the bases of paxillae to the relatively smoother (but still 

 wrinkled) skin of the actinal area ; and also by the limitation of the small papulae to the 

 area circumscribed by the abactinal plates. Along the interradial line between mouth- 

 plates and inferomarginals there are 10-12 actinal plates decreasing in size toward the 

 margin. 



The madreporite is 3 by 4 mm. and situated in middle of r ; surrounding it are 5 or 6 

 large paxillae, the largest with 19 spinelets. 



The tabulum of the major abactinal plates is distinctly higher (o-45-o-5 mm.) than in 

 ftisciis (o-i8-o-22 mm.) and is about the same as in a comparable specimen of charcoti. 

 The spinelets greatly resemble those of small specimens of charcoti but appear to be 

 slightly shorter (0-45-0-48 mm.). The longer actinal spinelets measure 0-58-0-7 mm., 

 and the sharp thornlets extend further toward base (Fig. A, 3-3 c). The spine sheaths 

 are about as pronounced as in fiiscus. The abactinal spinelets especially have a paxilli- 

 form appearance. Certain isolated spinelets or small groups, lower than the major 

 paxillae, may easily be mistaken for papulae. 



The adambulacral armature consists of 2 prominent spatulate furrow spines about 

 2 mm. long, the aboral the longer, placed slightly obliquely, edge to furrow. When 

 spines are upright the oblique furrow margin appears sometimes to carry 3 spines. 

 Subambulacrals usually 6, varying to 5 or 7, typically in 3 pairs parallel to furrow spines, 

 each pair successively shorter, the outermost being subequal to the adjacent actinals. 

 Near end of ray there are 7-9 spines to a plate (sporadically 10-12). The distal of the 

 2 furrow spines usually stands more prominently into the furrow and is more spatulate 

 than its adoral companion. 



