1915.] NATURAL SCIENCES OF PHILADELPHIA. 75 



d — Disk closely covered with granules; arms stout, 

 stoutest at base; numerous arm spines, 



OPHIODERMATIDiE, parS. 



dd — Disk usually free of granules; arms slender, stout- 

 est at a distance from base Ophiochitonid^. 



cc — Dental papillae well developed, forming a vertical 

 clump at apex of each jaw; disk often covered with 

 granules; arms stout, stoutest at a distance from base, 



Ophiocomid^. 

 Key to families of Chilophiurida (//) . 



A — Teeth not very stout, usually triangular; oral frames entire, 

 without well-developed lateral wings. 

 a — Second oral tentacle pores open more or less, or entirely, 



outside oral slits Ophiolepidid^, pars. 



aa — Second oral tentacle pores open within oral slits. 

 b — Disk squamated or tessellated, free of granules. 



c — Arms stout, stoutest at base; arm spines short, 



appressed Ophiolepidid^e, pars. 



cc — Arms slender, stoutest at a distance from base; arm. 



spines long, not appressed Ophiochitonid^, pars. 



bb — Disk covered with granules. 



d — Arms slender, stoutest at a distance from base; 

 arm spines few. 

 e — Arms inserted ventrally to disk; arm spines 



appressed Ophioleucid^. 



ee — Arms inserted laterally to disk; arm spines 



not appressed Ophiochitonid^, pars. 



dd — Arms stout, stoutest at base; numerous arm 



spines Ophiodermatid^. 



AA — Teeth very stout, quadrangular; oral frames with well-devel- 

 loped lateral wings. 



/-^No vertical clump of dental papillse. 



g — Arms stout, stoutest at base; arm spines 



short, appressed. Ophiolepidid.e, pars. 



gg — Arms slender, stoutest at a distance 



from base; arm spines long, not 



appressed Ophiochitonid.^, pars. 



// — Dental papillae well developed, forming a 

 vertical clump at apex of each jaw, 



Ophiocomid^. 



Family 1. OPHIOLBPIDID^ Ljungman. 

 (Characters as given above in keys.) 



Key to subfamilies of Ophiolepididce. 



A — Second oral tentacle pores open more or less, or entirely, outside 



oral slits Ophiomastin^. 



AA — Second oral tentacle pores open entirely within oral slits, 



Ophiolepidin^. 



