154 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



Diagnostic jeatures.- -The arm length is up to about 50 mm. in the known specimens 

 and the cirri up to XL, their length equal to about a quarter that of the arms, the 

 peripheral ones with up to 18, usually 16, segments, of which the longer proximal are 

 two to two and a half times as long as their median width and the distal are distinctly 

 longer than wide as well as very little wider dorsoventrally than the proximal ones; 

 P! has up to 25, usually 20, segments and is at least twice as long as P 2 , which is similar 

 to P 3 ; there are often calcareous patches in the perisome between the division series. 



Description.- Centrodorsal discoidal, thin, the rather broad dorsal pole very 

 slightly concave, 1 mm. in diameter. The cirrus sockets are arranged in two irregular 

 rows. 



Cirri XXVI, 14-16, from 12 to 14 mm. long, intermediate in character between 

 those of A. bifida and those of A. mediterranea. The longest proximal segments are 

 from two to two and a half times as long as the proximal diameter, slightly constricted 

 centrally; the short outer segments are usually half again as long as broad, becoming 

 slightly longer on the last three, with a perfectly straight dorsal profile. The opposing 

 spine is minute, terminal, and sharp. The moderate central constriction of the longer 

 earlier segments makes the outer ones, which are slightly flattened laterally, appear 

 broader in lateral view; but the difference is relatively slight. 



The perisomic areas between the IBr series are occupied by triangular masses of 

 rather solid perisomic plates. The disk is 7 mm. in diameter, and bears a very few 

 small calcareous nodules, more numerous on the base of the anal tube than elsewhere. 



The 10 arms are 35 mm. long and have a fairly smooth dorsal profile. The first 

 and second brachials are longer outwardly than inwardly; the first syzygial pair (com- 

 posed of the third and fourth brachials) is wedge-shaped, slightly longer inwardly than 

 outwardly. From about the tenth onward the brachials are triangular with a slight 

 tendency toward an overlapping of their distal ends. From the twentieth onward they 

 become wedge-shaped. The syzygial pairs are long. 



Syzygies occur between brachials 3+4, 9 + 10, and 14 + 15, and distally at intervals 

 of 3 or 4 muscular articulations. 



PI is very long, though not especially stout, about 10 mm. in length and composed 

 of 18 to 20 segments, of which the first is about as broad as long, the second is slightly 

 longer than broad, the third is slightly over twice as long as broad, and the remainder 

 are three times as long as broad; the third and following have very slightly produced 

 and very finely spinous distal ends. 



P a is similar, about 6 mm. long, with about 12 segments. 



P 2 is usually about one-third as long as P ]; composed of about 8 segments, of which 

 the three basal are broad and the remainder elongated. The immediately following 

 pinnules are of the same length, after which the pinnules become elongated and more 

 slender, reaching a length of 9 mm. distally. 



The color in alcohol is dirty white. 



Notes [BY A.M.C.]. A number of specimens from southwest of Sierra Leone, with 

 arms probably up to about 50 or 55 mm. in length, all have the centrodorsal with sloping 

 sides bearing about XL cirri and the small dorsal pole distinctly concave, measuring 

 0.7 to 0.9 mm. across when the total diameter of the centrodorsal is 2.5 to 3.0 mm. In 

 two specimens from off Accra, the centrodorsal is more discoidal, the dorsal pole being 

 1.6 to 1.8 mm. across and the total diameter about 3.4 mm.; in one the dorsal pole is 

 distinctly concave but in the other it is nearly flat. In all these specimens there are 



