OPHIURANS OF UNITED STATES NATIONAL MUSEUM. 67 



The arms, very slender, are extremely long and their length may even exceed 

 10 centimeters. I obserA-e but tliiee brachial spines even at the basis of the arms. 

 A. graciUima has been met with on the coast of South Carolina. 



AMPHIODIA (=AMPHIURA) ERECTA. new species. 

 Plate 6, fig8. 4-r. 



^Z6a<ross Station 2136. Feb. 29, 1884. Off Cape Hatteras. Lat. 17° 4.3' 40' 

 N.; long. 75° 38' 25" W.; 52 fathoms; co. brk. sh. Two specimens 



Type.— Cat. No. 32295, U.S.N.M. 



In the larger specimen the disk is somewhat oval and its diameter ranges 

 between 6 and 7 mm. The arms are twisted so that it is impossible to measure 

 exactly theii- length; two of them are entu-e and they could not have exceeded about 

 35 mm. The second specimen is much smaller and the diameter of its disk does 

 not exceed 3 mm., but the arms are comparatively longer and their length ranges 

 between 35 and 40 mm. I \vill describe this species from the larger spechnen. 



The disk is rounded and not at all notched 'n the interradial spaces. The upper 

 face is covered with middle-sized plates, which are fairly thick, a little unequal, little 

 imbricated, and become somewhat larger in the neighborhood of the radial shields; 

 there is not the slightest indication of primary plates. At the margin of the disk 

 certain plates carry a short, wide, and flattened spine vnth a rounded end; these 

 spines vary in number, but are always few, six or eight in each interradius, and they 

 do not form an interrupted row; most generally they are not observed until about 

 the middle of the interradial spaces, but in one of these spaces they extend to near 

 the radial shields. Some of these spmes, shorter than the others, even seem to be 

 a du-ect extension of the plate which stands erect; it then becomes difficult to tell 

 whether we have to deal here with a spine in the proper sense of the word or with a 

 small plate which stands erect. It is not so with the smaller specimen, where the 

 spines are more numerous and lying closer, and generally form a more regular row; 

 they are comparatively longer and more developed and consequently more distinct 

 than in the larger specimen. The radial shields are smaU and contiguous over most 

 of theh- length along their radial edge, which is straight, while the interradial side is 

 strongly convex; they are separated proximally on the fourth or third part of their 

 total length by a very narrow space. These shields are about tlu-ee times longer 

 than wide, their length being equal to about one-third of the disk radius. 



The plates of the upper face of the disk extend without interruption on the under 

 face which they cover entirely, and where they appear imbricated, rounded, and 

 subequal. The genital slits are narrow. 



The mouth shields, much elongated, are at least twice longer than wide; they 

 are lozenge-shaped, or more exactly suggest the shape of a boot sole, and their 

 widest part is somewhat nearer the distal than the proxknal end. They offer a 

 very rounded and wide proxuual angle, two antero-lateral sides which join by obtuse 

 and more or less protruding angles, the two posterior edges which are excavated; 

 the latter are miited by an angle, which is also quite rounded and wide and in 

 general truncated so as to represent a short distal side. The adoral plates, located 

 almost entirely on the sides of the mouth shields, have the shape of an elongated 

 and narrow triangle, with the three sides more or less excavated; these plate's are 



