1881 ] NATURAL SCIENCES OP PHILADELPHIA. 389 



gave an excellent description of the genus, and showed that the 

 arms in this type proceed from the radial openings as in other 

 crinoids, and that the interradial appendages are not arms at all. 

 They state that the true arms are always pendant, apparently 

 overlooking Hall's T. spinigeruSj but this is not uniformly the 

 case even in the Carboniferous species, as we afterwards dis- 

 covered in Hall's T. tuberculosus, (see Proc. Phila. Acad. Nat. 

 Sci., 1878, p. 262), whose arms stand erect, and fold over the 

 dome. We also found the ventral furrow of the arms to be always 

 on the inner side of the arm, next to the body, and accordingly 

 on reverse sides in the erect and the pendant arms. It is pos- 

 sible that this feature may warrant a subdivision of the genus, 

 but until we are better acquainted with the arms in the majority 

 of the species we shall not attempt it. 



Meek and Worthen proposed to arrange the British and 

 American species under two sections, based upon the different 

 positions of the so-called false arms, whether placed above the 

 interradial regions as in the latter, or more radial as in the 

 former. We do not attach much importance to this variation, 

 especiall}- in view of our interpretations of the relations and 

 functions of these appendages, besides there is considerable 

 variation in this respect among the American species. The arm 

 openings are in some cases located well under the overhanging 

 margins of the bases of the false arms, in others on either side 

 of them. In no case, however, among American specimens have 

 the false arms been observed to be directly over the ray, as 

 represented in Phillips' diagram of G. bursa, and we are by no 

 means satisfied that such was actually the case in the British 

 species, for sometimes the basals alone are prominent and spinif- 

 erous, sometimes only the first radials, and it is possible that in 

 some cases they have been confounded. 



Some authors, notabl}' Meek and Worthen, object to Cum- 

 berland's name OUacrinus because it w^as not accompanied by 

 any diagnosis or specific name, and give precedence to Gilbertso- 

 crinus, the generic and specific descriptions of which disclose no 

 characters to distinguish the genus from Rhodocrinus, and which, 

 moreover, entirel}^ overlooked the real characteristic features of 

 this type. Cumberland's published figures give a distinct 

 exposition of essential characters, which leave no room for 

 doubt as to the type represented, and under the rules adopted by 



