1915.] NATURAL SCIENCES OF PHILADELPHIA. 69 



Subfamily 1. OPHIACTININ.^ nov. 



(Characters as given above in key). 



This subfamily includes Ophiactis. Hemi-pholis,^ Ophiopus and 

 OphiophoUs. 



Subfamily 2. AMPHIURIN^. 



(Characters as given above in key.) 



This subfamily includes Amphioplus, AmphiUmna, Amphiodia, 

 Ophiophragmus, Ophiocnida, Amphipholis, Ophiostigma, Amphiura,^ 

 Ophionema, Paramphiura, Ctenamphiura, Ophiocentrus,^ etc. 



The first two genera may be grouped as an Ariiphiophi s-group, 

 the next three as an Amphiodia-group, the following two as an 

 AmphiphoUs-group, and the last five as an Amphiura-group. The 

 Amphipholi s-gvoup are very easily distinguished, while the other 

 three groups are less so. These groups may be distinguished as 

 follows : 



Three classes of oral papillse may be recognized: the first arising 

 from the adoral shields, the second from the oral plates, and the 

 third from the dental plates and being infradental in position. A 

 papilla, which arises partially from the adoral shield and partially 

 from the oral plate, is referred to the second class. Now, let +1 

 indicate the presence of papillae of the first class, —I the absence of 

 same; +11 the presence of papillae of the second class, etc. Then, 

 the groups of genera are formulized as follows: 



Amphioplus-group = +1 +11 +III. 



Amphiodia-group = — I +11 +III. 



Amphipholis-group = — I +11 +III. 



A7nphiura-group = +1 ±11 +III. 



It may clearly be seen that the A?7iphiodia-group are not inter- 

 mediate between Amphioplus- and Atnphiura-group, but are, say, 

 the A)nphioplus-group without the papillae of the first class, while 

 the Amphiura-group are the Amphioplus-group without all or most 

 of the papillse of the second class. I believe that certain species 

 having two distal papillae, usually referred to Amphiodia, are really 

 referable to Amphiura. 



Apphang the same principle to the Ophiactininae and Ophio- 

 trichidae, we have the following formulae: 



2 Hemipholis rnicrodiscus Duncan, 1870, is evidently a genuine Amphiura. 

 * Including Ophionephthys. 

 5 Including Amphiocnida. 



