68 BULLETIN 84, UNITED STATES NATIONAL MUSEUM. 



extremely narrowed inwardly, and they are not contiguous on the interradial median 

 line; they grow wider outwardly, but nevertheless remain widely separated from the 

 opposite plate by the first under brachial plate. The oral plates are small and 

 triangular. The oral papillie amount to three on each side; they are rather obtuse 

 and have about the same shape; the middle one is, however, a little smaller than 

 the other two, the external one is a little widened and triangular, the internal one 

 is more elongated but not very thick; these three papillte are contiguous and they 

 form a regular row. In the smaller specimen they are uniform, rather short, and 

 flattened. 



The upper brachial plates are extremely large and very much widened, almost 

 three times wider than long; they are quadrangular, with a slightly rounded proximal 

 side, an almost straight or even slightly depressed distal side, and short lateral sides, 

 which join the two other sides by rounded angles. They are all widely contiguous. 



The first under brachial plate is fairly large, transversely widened, trapezoidal, 

 with a narrow proximal side, a wider distal side and lateral sides which are divergent 

 and excavated. The succeeding plates are very large, pentagonal, much wider than 

 long, with a very obtuse and rounded proximal angle, slightly divergent lateral sides 

 joining by rounded angles the distal side, which is wide and generally a little notched 

 in the middle; the proximal angle may even completely disappear on the first plates, 

 which then become quadrangular. All these plates are contiguous. 



The lateral plates, little protruding, each bear thi'ee subequal spines which are 

 equal to the article; they are wide, flattened, with a plainly rounded end. 



The tentacular scales lie at a right angle; thej^ are equal and semicircular. 



The color of the specimens in alcohol is whitish. One can detect, on the upper 

 face of the arms in the larger specimen, a median longitudinal line of a very light 

 brown, and here and there some slightly darker annulations, each of which covers 

 two articles. 



Connections and differences. — Owing to the arrangement of the oral papillae, 

 which are three in number and subequal, this Amphiura pertains to the section 

 Amphiodia of VerriU. It can not be mistaken for A. liitkeni (Ljungman), which 

 bears, on the margin of the disk, some conical, elongated, and sharp-pointed spines, 

 and has its disk covered with very fine plates; the radial shields and the two tentac- 

 ular scales are more developed in this species than in A. erecta, and the arms are 

 extremely long. Further on I shall deal with A. liitkeni, which also must be classified 

 in the section Amphiodia. 



A. erecta closely resembles A. nisei Liitken, to which is it akin by the shape of 

 the mouth shields and by the upper and under brachial plates being very wide ; but 

 the former differs from the latter by some short, obtuse, and flattened spines standing 

 at the margin of the disk, as well as by the radial shields, and also the upper plates 

 of the disk being smaller, the adoral plates being narrower and more elongated, and 

 the brachial spines being a little longer. 



As I wanted, nevertheless, to compare my species more thoroughly with A. riisei, 

 I have been temporarily entrusted, thanks to the kindness of Mortensen, with the 

 specimen wliicli was first described by Liitken under the name of A. cordifera, 

 and to which he gave, aftei'wards, the name of A. riisei. I can add a few 

 remarks to Lutken's description. The plates of the upper face of the disk of 



