OPHIURANS OF UNITED STATES NATIONAL MUSEUM. 49 



introduced by Ljungmau, was novor described by him and we know it only by the 

 very short comparison which he made between the said species and A. latispina. 

 These two species belong, together with A.Jlexuosa and A. semiermis, to the group 

 wliich Ljungman had separated from the other Amphiuridse under the name of 

 Ilemilepis, owing to the lack of plates on the under part of the disk. It se*ms 

 useful to me to describe with some detail A. latispina, so as to possess the elements 

 of a comparison with the species which I describe below und«T the name of A. hin- 

 bergiensis. 



In Ljungman's type the disk is about 7 mm. in diameter, measured between 

 two nonconsecutive angles of the disk, and one of the sirms is preserved to a length 

 of nearly 40 mm. 



The disk is very strongly excavated in the interradial spaces. The upper face 

 is not unifomdy and completely covered with scales, for there is in the middle of 

 each interradial space one triangidar region which remains bare. The plates appear 

 first in the central region where they are imbricated, small and equal, and they 

 continue in the direction of the radii, so as to surround each pair of radial shields 

 with a certain number of rows; these plates grow larger and larger as they get nearer 

 to the radial shields. As a rule, the interradial spaces are bare, as I have just 

 stated, but in two of them I observe four or five little rounded plates which are 

 transparent and not in contact. The appearance of the upper face of the disk of 

 this Am/pMura is consequently rather pecuhar. The radial shields are pretty large, 

 elongated, narrow, four or five times longer than wide, and \vider distaUy than 

 proximaUy; they join distaUy on one-third of their length, and, proximally, they 

 go progressively apart from each other without, however, becoming very divergent. 

 The very narrow interval which separates them is also quite bare. The length of 

 these shields is almost equal to half the radius of the disk. 



The under face of the disk in the interradial spaces is bare; however, in one of 

 these spaces I notice a few rounded j^lates, which are isolated, very thin, and identical 

 with those which I have reported above in the interradial spaces of the upper face. 

 The genital plates are narrow and elongated and the genital slits are quite apparent. 



The mouthpieces are disposed as m. A.Jlexuosa, and the mouth sliields, especially, 

 have exactly the same shape as in that species. They arc triangular, \\\i\x a very 

 convex proximal side, concave lateral sides, and a truncated distal apex, which 

 forms a small rounded edge ; they are as long as wide or slightly longer than ^vide. 

 The adoral plates are triangular, with more or less concave sides, and they arc not 

 contiguous on the interradial median line; but stiU they are more developed out- 

 wardly than in A.Jlexuosa and come very near the median line, so that they compress 

 the first under brachial plate rather strongly between them. The external oral 

 papiUa is strong, conical, and elongated, perhaps a little thicker and proportionately 

 somewhat shorter than in A.Jlexuosa. 



The first upper brachial plates have also almost the same shape as in A.Jlexuosa. 

 They are oval and rather small, owhig to the overgi-owth of the lateral plates; the 

 lateral margms are very convex, and the proximal side, less convex, is often broken 

 into two distinct edges joined by a very obtuse angle. They are a little wider than 

 long and thev all remain broadly in contact. 



