OPHIUBANS OF UNITED STATES NATIONAL MUSEUM. 135 



The genital slits are already apparent. The under brachial plates are separated 

 by the lateral plates. 



Connections and differences. S. murrhina was described by Lyman from a 

 specimen, the diameter of which was 12 mm.; I do not think it possible to refer to 

 that species the two specimens dredged by the Albatross, nor the young specimen 

 from the Bahama expedition, as Verrill has done, for the arrangement of the plates 

 of the upper face of the disk is very different. In fact, S. murrhina shows a distinct 

 central rosette, and all the upper plates of the disk are coarsely tuberculous, but 

 it does not offer the slightest indication of that large radial plate which is provided 

 with a conical protuberance, nor of the similar plate which succeeds the former, 

 both of which plates are characteristic of S. conifera. In the latter, the central 

 rosette is already dissociated in a specimen which has a disk not exceeding 5.5 mm. 

 in diameter. In S. murrhina, the disk itself is flattened and not thick and swollen; 

 the upper brachial plates are transversely oval and not triangular; the shape of the 

 mouth pieces and of the genital slits also differs in the two species. The arms also 

 seem to be longer in S. murrhina, but this might be due to a difference in size. 



In S. lineata Liitken and Mortensen from the Pacific, the upper plates of the 

 disk are neither tuberculous nor protruding, and the brachial spines are three in 

 number. 



SIGSBEI A SEXR ADI AT A, new species. 

 Plate 17, figs. 4-5. 



Albatross station 2753. Dec. 4, 1887. Lat. 13 34' N.; long. 61 03' W.; 281 

 fathoms; bk. s.; temp. 48 F. Two specimens fixed on a branch of coral. 



Type Cut. No. 32308, U.S.N.M. 



Both examples are very small and the diameters of the disk do not exceed, 

 respectively, 2 and 1.5 mm.; however, they display characters sufficiently plain to 

 allow of their being described and they are at once noticeable by the number of their 

 arms, which are six. In the larger specimen four arms only are preserved, the other 

 two being broken at their base; of the preserved arms, two are wider and a little 

 longer than the others; all these arms are strongly rolled up and it is difficult to 

 estimate their length which certainly does not reach 7 or 8 mm. In the smaller 

 one, three arms only are preserved, one of which is smaller than the others. 



The disk is circular, rather thick, with a rounded outline; it is depressed in its 

 central region which is beset by a dozen small, polygonal, unequal, and irregularly 

 arranged plates; there is not the slightest indication of a primary rosette. Out- 

 wardly come the radial shields, which form an uninterrupted circle ; these shields 

 are large, triangular, one and a half times longer than wide, with a rounded proxi- 

 mal angle and a concave distal side; the two shields of each pair are contiguous on 

 the whole length of their radial side, and each pair is contiguous with two neighbor- 

 ing pairs. Each radial shield is succeeded by a large, rounded, and globulous plate, 

 which is wider than long and sometimes divided into two successive parts ; the two 

 plates of each pair are generally separated by a narrow interval which allows the 

 first upper brachial plate to be seen, while, on their external side, the plates are more 

 approximated to the next ones or even are contiguous with them. These plates 

 form the lateral faces of the disk and they extend over to the under face where 

 6061 Bull. 8414 10 



