remarkable OpMuridfrom Brazil. 369 



the British Museum, are three examples of a remarkable 

 Ophiuridj to which I should like to direct the attention of 

 naturalists who may be collecting in Brazilian or West -Indian 

 waters. The form is, in the first place, remarkable for the 

 extraordinary length of the arms in proportion to the dia- 

 meter of the disk, for while the latter measures about 4 millim., 

 the arms are no less than 150 millim. long. ; the proportion 

 of arm to disk is therefore as 1 : 37'5, or more than twice 

 that of Ophiothrix longiiJeda. which Mr. Lyman gives as 

 1:18. 



It is, unfortunately, impossible to be certain of the genus 

 to which tliis very long-armed form is to be referred, for from 

 all three examples the covering of the disk has been lost, and 

 this loss has, in a very curious way, affected also the dorsal 

 surfaces of the most proximal arm-joints. The loss of tliis 

 upper surface would, if it were natural (and the close simi- 

 larity between the specimens leads one to imagine that it is 

 so), be more or less fatal to the animal in inverse proportion 

 to the quantity of carbonate of lime which, in the form of 

 covering-plates, ordinarily protects the disk. On the assump- 

 tion that that quantity is small, or that the greater part of the 

 disk is naked, the species now under consideration appears to 

 be allied to the genera Ophionema and Ophionephthys of 

 Dr. Liitken. In these genera the arms are likewise long, 

 though by no means so extraordinarily long as in the Bra- 

 zilian form, and they are both represented in the West- 

 Indian seas. Naturalists who have the opportunity of 

 observing this long-armed form in life should direct particular 

 attention to this loss of the disk, with a view to answering 

 sucli questions as whetlier the loss is in any way associated 

 with the act of reproduction, whether the disk becomes 

 restored, and, if so, whether the restoration is effected rapidly. 



As it is convenient to have a name for our object, the species 

 may be provisionally placed in the genus Ophionephthys * 

 and be called 0. sesquipedalis. The following description 

 will probably serve the collector as a means of identifying 

 it:— 



Disk very small ; arms narrow, exceedingly long, and pro- 

 bably, when complete, as much as forty times the diameter of 

 the disk ; three short arm-spines, one tentacle- scale. Upper 

 arm-plates very regularly oblong, the proximal and distal 

 edges quite straight, about three times as wide as long. 



* If it should be found that this is its proper place it will be necessary 

 to so far amend the diagnosis of that genus as to diminish to two the 

 number of the mouth-papillse and to three the number of the arm-spines. 



