MONOGRAPH OF JAPANESE OrHIUROIDEA. 3 



being flmily united together ; the peristoniial plates are entire and 

 more or less soldered to the oral frames ; &g. Tlie vertebrœ 

 are very short and stout and have streptospondyline articulation ; 

 and all or some arm spines are converted into compound hooks. 

 E. g. Ophiohyrsinœ mihi ; Trlcliasteridœ mihi ; Gorgonocephalidœ, 

 OphiaccmtJiidœ pars ; Hemieiiryalidœ mihi ; OphiopJioUs ; and 

 Opliiotrichidce pars (certain forms, as OphiophoUs and Ophiotrichidœ 

 pars, in which the tendency of coiling of the arms is not very 

 strong, have, however, rather zygospondyline articulation of the 

 vertebrae). 



2. The more or less divided vertebrae are found only in 

 certain genera with horizontally flexible arms, but never in those 

 forms in which the arms are capable of being coiled vertically. 

 These two results are evidently serious objections to Bell's classi- 

 fication, because the greater part of Bell's Streptophiurce have, 

 according to my own observations, horizontally flexible arms and 

 more or less divided vertebrae, of which the articulation is typically 

 zygospondyline, instead of being " primitive streptospondyline."^-' 

 For the same reason, I am unable to believe that, Geegoey's 

 Palaeozoic Streptophiurce, or Stüetz's Protophiurce have strepto- 

 spondyline articulation of the vertebrae. 



3. The more or less divided vertebra} are of two kinds. 



a. Those which are divided into halves by a single fusiform 

 pore, are found in those forms in which the dorsal side of 

 the arms is more or less unprotected. E. g. Opliiohelus ; 

 Oplilogercn ; Ophiosclasma ; Ophiostiba ; Opliiohyaliis ; 0- 

 phiomyxa ; &c. 



1) As to the imperfection of Bell's classification, see the following i)fipers : — Igebna 1>. J. 

 SoLLis, On Onychaster, a Carboniferous Brit tie- Sta r ; Philos. Transact, Ser. B, Vol. 204, 1913;— 

 Th. Mobtensen, On the Alleged Primitive Ophinroid, Ophioteresis elegnns Bell, &c. ; Mindeskr. 

 for .Tapetxjs Steenstrup, 1913. 



