1881.] NATURAL SCIENCES OF PHILADELPHIA. 313 



Miller's tj'pical species, with a single exception, belong to the 

 same division, and his A. triacontadacttjlus and A. j)oly dactyl us 

 must form the t3pes.' The genus Actinocrinus, as amended by 

 Meek and Worthen, and as it is now understood, embraces almost 

 the majority of all European Actinocrinidae, while it includes in 

 this country, although represented by even more species, only a 

 comparatively small portion of the general representation of the 

 famil}'. 



Meek and Worthen, after carefully restricting the genus, sepa- 

 rate it in vols, ii and v of the Illinois Report into two sections : 



A. The arms given otf directly from the body and forming a 

 continuous ring around it ; the divisions of the ray taking place 

 in the calyx proper, which has a more or less subconical form. 



B. The radials, from the third primary up, bend abruptly out- 

 ward, forming protruding lobes, which at the interradial spaces 

 produce deep sinuses. The divisions take place in the lobes, 

 which frequently are extended into free rays, and these giving off 

 the arms. 



Looking at the species of the two sections, and particularl}- at 

 A. proboscidialis with only twenty arms on the one hand, and A. 

 Loivei with fifty or sixty arms on the other ; these distinctions 

 seem to acquire almost generic value ; but comparing species with 

 a njore nearly equal number of arms, it will be found that the 

 division cannot be carried out practically, at least not among 

 the European species, which in the majority of eases form alink 

 between the two extremes of the American species. 



The genus Actinocrinus has frequently been confounded with 

 Batocrinus, and neither Casseday, the founder of the latter, nor 

 Meek and Worthen, who recognize it, have pointed out any dis- 

 tinctions which warrant their generic division. Such, however, do 

 exist, as we hope to prove. 



In Actinocrinus and other Actinocrinites, the anal area, as a 

 rule, has but a single special anal plate, and this located between 

 the two first primary radials. There are two plates in the second 

 series which are in line with — and take the place of — the larger first 



' Roemerinl855 restricted the genus Actinocrinus to the Subcarbon- 

 iferous, and included in it only such species which at the arm regions are 

 provided "mit rundlichen Falten," and in which the vault is elevated 

 and extended into a proboscis. He refers all Silurian and Devonian 

 species previously described under Actinocrinus, to distinct families. 



