OPHIUKANS OF UNITED STATES NATIONAL MUSEUM. 47 



The upper brackial plates are not very large; they are as a whole rounded or 

 oval, and they can hardly be said to have distinct sides ; they offer a narrow proximal 

 side which is slightly excavated at the beginning of the arms and a strongly convex 

 distal side. The first eight or ten plates are rather small, almost as long as wide; 

 they become progressively larger and at the same time wider than long. 



The first under brachial plate is small, trapezoidal, with a widened proximal 

 side, a narrow distal side, and diverging lateral sides; it is a little wider than long. 

 The succeeding plates are middle-sized and rather narrow; they are quadrangular, 

 a little longer than wide, with rounded angles, a little more widened in their proximal 

 region; the proximal side is actually divided, at a short distance from the basis, 

 into one fairly wide median side and two little oblique lateral sides. All these plates 

 are contiguous. 



The lateral brachial plates carry six spines each as indicated by Ljungman. 

 The first ventral spine is about as long as the article; it is fairly thick, cylindrical, 

 with a rounded point. The following one is a little larger; it is fairly wide at its 

 basis, but it rapidly grows thinner and its point is sharper than that of the foregoing 

 one. Afterwards, the length of the spines decreases very slowly down to the 

 last dorsal one which is lightly flattened but sharp, a shape which was already 

 beginning to appear in the preceding spine. The end of the lateral spines is simply 

 pointed and absolutely straight; it is neither truncated nor bent sideways into a 

 little hook, neither is it provided with spinules; their surface is perfectly smooth 

 on their whole length. The exact shape of the brachial spines of A. flexuosa has 

 been correctly observed by Ljungman and in the table of the species of Amphiuridae 

 published by him in 1871, he sets A. semiermis and flexuosa which have "spinse 

 brachiales acuminatse, non complanatae, teretes" in opposition to A. latispina 

 and kinbergi which have "spinse brachiales obtusse, plus minus complanatae, 

 latiusculas." 



The tentacular brachial pores, rounded, are very large while the tentacular 

 scales, amounting to two, are extremely small ; these scales are rounded and arranged 

 oblique to one another; the external scale, which is inserted on the lateral plate, 

 is a little larger than the other and tends to assume an oval shape. These scales 

 do not really take their definite characters until after the first two or three brachial 

 articles on which they may either be lacking or limited to one only. 



The color of the specimen in alcohol is whitish on the upper face and brownish 

 on the under face. 



Connections and differences. The species of the genus AmpMura (e. lat.) are, 

 generally, separated from one another by very obvious and easily distinguishable 

 characters ; if it has sometimes been found difficult to determine them, it has been 

 due more to insufficient descriptions and to the lack of drawings than to the 

 existence of intermediate forms. If we abide by the characters which we have 

 just observed in Ljungman's type, which is evidently the only one which can be 

 taken as a standard, we shall say that A. flexuosa is distinguished by the fol- 

 lowing chief characters: 



1. The under face of the disk is bare, the upper plates pass over somewhat 

 to that face in the shape of a marginal and rather narrow border, but the said face 

 may be considered as remaining bare ; a like border is often observed in other species 



