370 A. M Verrill — North American Ophhcroidea. 



They bear a short row of small rough spines or tentacle-scales ; 

 above them are double vertical rows of small plates, forming raised 

 ridges and bearing granules and also rows of minute glassy hooks, 

 on the sides and top of the arms. These sometimes extend on the 

 radial ridges of the disk. 



Teeth and tooth-papillse numerous, spiniform ; the latter form an 

 apical cluster. Oral papillae similar in form, sometimes lacking. 

 The teeth may form double vertical rows. 



This family includes Astrochele, Astrogomphus, Astroporpa^ and 

 Astrotoma all with simple arms, and Astrocnida with the arms 

 forked near the ends. 



Family, ASTROSCHEMID-ffi Vemll. 



Astroschemidce Verrill, Opliiur. Bahama Exped., v, p. 76, 1899. 



Arms simple, long, slender, coiled. Disk five-lobed, with ten 

 radial ribs ; naked or granulated. Radial shields narrow, usually 

 elongated. Under arm-plates small. Upper arm-plates poorly 

 developed, often wanting, sometimes represented by two or more 

 pieces, covered by naked skin or granulated. Side arm-plates rela- 

 tively large, covering a large j)art of the lower side of the arm, and 

 usually bearing two elongated spines or tentacle-scales. 



Teeth are large, stout, several in a vertical row. Oral papillae are 

 small or wanting. 



Oral and adoral plates, regularly formed, but covered by cuticle. 

 Genital slits short, situated near the outer margin of the disk. 



Internal mouth-frames strong, well developed, but without wing- 

 like processes. 



This family includes Astroschema, Astrocreas, and Ophiocreas. 



Family, ASTRONYCID-ffi Verrill. 



Astronycina (pars) Ljung., Oph. Viv., 1867. Bell, Cat. Brit. Echin., p. 27, 



1892. 

 AstronycMce Verrill, Ophiur. Bahama Exped., Bull. Univ. Iowa, v, p. 74, 1899. 



Arms undivided, long, slender, coiled, not annulated nor granu- 

 lated. Disk with ten narrow radial ridges formed by long narrow 

 radial shields, covered with thin, smooth scales or naked skin. 



Upper and under arm-plates rudimentary or absent. Side arm- 

 plates cover most of the lower side of the arm and project laterally, 

 bearing two, three, or more spines or tentacle-scales, which may be 

 either simple or hook-like. The genital slits are short, near together 

 in a depression near the oral shields. 



