414 On a new Genus of Echinodermata. 



specimen, which are modified arm-spines belonging to the 

 side arm-plates, whilst those in Ophiojyhyttum are, so far as 

 I am able to judge from the figure alone, simply disk- 

 spinelets attached indiscriminately to radial and interradial 

 plates alike. 



Without reviewing in further detail the structural pecu- 

 liarities of this abnormal Echinoderm, it will be clear that no 

 group of genera or family hitherto known can include a form 

 of such aberrant type within the present limits of definition. 

 Astrophiura consequently stands apart, and, in a classificatory 

 point of view, must be considered as the representative of a 

 family of which it is, as yet, the only member known. 



Regarding the serial position which the Astrophiuridge 

 would occupy amongst Echinodermata in relation to the 

 accepted arbitrary divisions in present use, they will natu- 

 rally be placed, by logical reasoning from the structure of 

 the present form, intermediate between the Ophiuroidea and 

 Asteroidea. Respecting the affinities of Astrophiura, the con- 

 clusion seems inevitable that they apparently point to Ophiu- 

 roid ancestry, whilst the modifications from the true Ophiuvoid 

 arrangement which are present unquestionably take the direc- 

 tion of the more centralized Asteroid plan of organization, 

 and thus form a step which diminishes the distance of struc- 

 tural difference which has been considered to separate the 

 two orders : upon such grounds Astrophiura has a due claim 

 on the consideration of systematists as an intermediate and 

 connecting form. It is undoubtedly premature, in the present 

 state of our information, to endeavour to indicate absolutely 

 how far Astrophiura bridges over the differences between 

 Asteroids and Ophiuroids ; but it is certainly not too much to 

 say that this genus passes very much further over the border- 

 land than any other Echinoderm with which we are at present 

 acquainted. 



The following diagnosis will embrace the characters in- 

 volved in the preceding description : — ■ 



Fam. Astrophiuridge, mihi. 



Brachia cum disco ophiurano in corpore pentagonali iuclusa. Dentes 

 absunt. Oris armatura simplex et imperfecta. Fori pedum 

 ambulacraliuni septis angustis ad perpendiculum radii dircctis 

 disjuncti. Cava interbrachialia perlata. 



Astrophiura per mir a, gen. et sp. nov. 



Corpus pentagonale, depressum, supra convexum. infra paulo con- 

 cavura, obtectum squamis conciimis et plains, in dimidio inte- 

 riore more disci ophiurani dispositis, in dimidio exteriore scutella 



