380 ART. 2. — H. MATSUMOTO : 



paedomorphic characters are not always archetypal, is clear from 

 what I have said already. 



In my opinion, the Opliiarachnince and Ophiochltonince are the 

 most archetypal of the Chilopliiurlda, some of them being so near 

 to the Ophiacanthidce as to be distinguished from the latter only 

 with great difficulty. Indeed Opliiuroconis and Ophiurochœta have 

 hitherto been confused with Ophiolimna of the Ophiacanthidce by 

 several authors, and Ophiochiton was considered by Verkill to 

 belong to the Ophiacanthidce, Moreover, I have been able to 

 find out incompletely divided vertebrae in certain species of 

 OphiuroGonis and Ophiurodon. 



A next ally of the Ophiarachnince is, of course, the Ophioder- 

 matinœ, which are distinguished from the former by the very 

 short arm spines. Judging fi'om the degree of calcification of the 

 vertebrae, the Ophiarachnince ■ are evidently more archetypal than 

 the Ophiodermatinœ. The Ophiochitonince lead to the Ophionei'ei- 

 dince, which are however a step more specialised than the former 

 in having a well developed masticatory apparatus. Ophiodoris is 

 evidently intermediate between the Ophiochitoninœ and the other 

 Ophionereîdinœ. The Ophionereidince are intermediate between the 

 Ophiochitoninœ and Ophiocomidce, so far as the oral skeleton is 

 concerned, and might fairly be looked upon as the direct ancestor 

 of the last mentioned family, if the dorsal surface of the vertebrae 

 were not so strongly notched at the inner end. This last character 

 of the vertebrae of the Ophionereidince, as well as probably of the 

 Ophiotrichidœ, appears to me to be correlated to the very high 

 flexibility of the arms. The same character is not however equally 

 well developed in all the Ophionereidince, but only very feebly in 

 Ophiodoris, wliich is unique among the Ophionereidiiue in being 

 destitute of supplementary dorsal arm plates. A parallel character 



