OPHIURANS OF UNITED STATES NATIONAL MUSEUM. 49 



introduced by Ljungman, was never 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.flexuosa and A. semiermis, to the group 

 wlu'ch Ljungman had separated from the other Amphiuridae under the name of 

 Hemilepis, owing to the lack of plates on the under part of the disk. It seems 

 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 under the name of A. Tcin- 

 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 arms is preserved to a length 

 of nearly 40 mm. 



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

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

 each interradial space one triangular 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 Amphiura is consequently rather peculiar. The radial shields are pretty large, 

 elongated, narrow, four or five times longer than wide, and wider distally than 

 proximally; they join distally 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 plates, 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 in A.flexuosa, and the mouth shields, especially, 

 have exactly the same shape as in that species. They are triangular, with 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 wide. 

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

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

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

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

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

 somewhat shorter than in A.flexuosa. 



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

 They are oval and rather small, owing to the overgrowth of the lateral plates ; the 

 lateral margins 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 they all remain broadly in contact. 



