On a new Form o/'Ophiuridae/rom New Zealand. 305 



Summary. 



The general results of the researches briefly detailed above 

 may be summed up as follows. 



The mandible has, as far as ascertained, essentially the 

 same structure in Rhizodopsis as in Rhizodus. In both, the 

 dentary element is narrow and pointed posteriorly, its upper 

 margin bears one row of small teeth, while at the symphysis 

 it is peculiarly thickened where it bears the first or anterior 

 laniary. This bone, turned upside down, has, in Rhizodopsis^ 

 been previously considered to be the prajmaxillary ; the last- 

 named element of the skull of that lish has now, however, 

 been ascertained to be a diiferent bone, which is quite similar 

 in form and relations to the prtemaxilla in other Crosso- 

 pterygii. 



The laniary teeth behind the anterior one are borne upon 

 separate internal dentary ossicles, which, Avhen the constituent 

 elements of the lower jaw are broken up and separated, will 

 also become disarticulated and dispersed. This is absolutely 

 proved in Rhizodus, and may be considered morally certain 

 in Rhizodopsis, though a clear view of the inner aspect of the 

 complete mandible of the latter, with the posterior laniary 

 teeth in situ, has not yet been obtained. 



Below the dentary the inferior margin of the jaw is formed 

 by a series of infradentary plates, while posteriorly the arti- 

 cular region is covered by a plate corresponding in position 

 apparently both with the angular and supraangular elements. 

 I may add that, in one specimen of Rhizodopsis, I have seen 

 very distinct evidence of a splenial. 



The great complexity of the structure of the mandible in 

 these forms and in the allied " Dendrodonts " of the Old Red 

 Sandstone need not astonish us when we take into account the 

 remarkably segmented splenial of the recent Amia, or the simi- 

 larly segmented maxilla of Lepidosteus. 



XXVI. — Descrijytion of a new Form of Ophinvidse from New 

 Zealand. By Edgar A. Smith, F.Z.S., Zoological Depart- 

 ment, British Museum. 



[Plate XV.] 



There are three specimens of this very remarkable form of 

 Ophiuridse in the British Museum — one presented by Major 



