OPHIUBANS OF UNITED STATES NATIONAL MUSEUM. 79 



meaning adopted by Verrill, afterwards take on the characters of the genus Ophien- 

 todia of the same author. 



The upper brachial plates are rather small, triangular, with a widely opened 

 proximal angle and a strongly convex distal side ; they are wider than long and sepa- 

 rated by a fairly long interval. 



The first under brachial plate is small, trapezoidal, narrower in its proximal 

 than in its distal part, with diverging lateral sides. The second one is large, very 

 much widened distally, with an obtuse proximal angle, diverging lateral sides, and 

 a very convex distal side, which may sometimes present, in its middle, a very small 

 and feebly protruding, widened median lobe. On the following plates the width 

 slightly decreases and the distal side becomes more strongly convex; therefore, the 

 plates become longer than wide, at the same time as the proximal angle becomes 

 more open. This elongated form of the under brachial plates is quite striking, and 

 in the young specimens these plates are seen to become sometimes even almost twice 

 longer than wide. I usually notice, on the under face of the plate, within the distal 

 side and parallel with it, two or three concentric striae, which are rather wide apart. 

 The under plates always remain separated by a narrower interval in the adults than 

 in the young. 



The lateral plates bear on their somewhat swollen distal side seven or eight 

 spines of increasing length from the first, which is almost equal to the article, to the 

 last one, which may reach the length of two and a half articles. These spines 

 are provided with fine and close denticulations in the young, which, however, are 

 less apparent in the adult, where they nevertheless remain visible through the 

 microscope. 



The tentacular scale is fairly large and wide, somewhat lanceolate, with a very 

 rough end. On the larger specimens this end is simply rounded, but on the two 

 smallest specimens, the diameter of the disk of which does not exceed 5 mm., this 

 scale is narrower and sharper, more so in one of them than in the other; in all the 

 others the tentacular scale displays the form which I have just indicated. On the 

 large specimens the tentacular brachial pores of the first pair always carry two 

 scales. 



Owing to the presence of distinct plates on the upper face of the disk, this 

 species ought to be classified in the genus OphwrnitreOa, if Verrill's classification 

 be strictly adhered to. On the other hand, we have seen that the oral papillae 

 are losing their regular arrangement with age; they may also become more numerous 

 as the number of the dental papilla? increases, such being the case in the species 

 classified by Verrill in his genus Ophientodia. 



When studying the descriptions and drawings of Ophiacaniha nodosa published 

 by Lyman, the question may be asked what are the characters on which that author 

 has based the separation of that species from 0. anomala. The most important 

 difference which I find refers to the under brachial plates, which, according to Lyman, 

 are a little wider than long, but it must be remembered that Lyman had at his 

 disposal but one specimen, the arms of which were broken near the disk, and conse- 

 quently he was unable to observe the changes in the form and elongation of the 

 successive under brachial plates, so that it is very difficult to take this character 

 into account. Therefore, the two species seem to me very likely to be synonyms. 



