SYSTEMATIC PART. 159 



one ; the remaining ten genera have simple radials throughout. Neither do 

 we find any remarkable development of certain radials, except when these 

 are compound. All this is seriously in the way of making the presence or 

 absence of infrabasals a subordinal character. 



Bather claims that among the Dicyclica departures from the pentameroua 

 symmetry of the cup plates occur only in the right posterior radial. Excep- 

 tions to this, however, are found in Atelestocrinus and Nanocrinus^ in which 

 the symmetry is disturbed by the anterior radial, and in the latter genus by 

 the right antero-lateral together with the anterior. 



Bather's researches were largely devoted to the Dicyclica of the Niagara 

 and Wenlock age. which he divided into three principal families : the " Den- 

 drocrinidge," the " Cyathocrinidae," and the " Decadocrinidae ; " and in addi- 

 tion to them he recognized two smaller families, the ^^ Euspirocrinidae " and 

 " Carabocrinidse," the latter unrepresented in Europe. 



The Dendrocrinidse are defined by him as follows : '^ Dicyclica, with R 

 alone, or with anal x alone, or with R and anal x, or with a radianal, anal 

 X and one plate of the tube, in the anal area of the dorsal cup ; with broad 

 radial facet ; with dichotomous arms, that may or may not develop pinnules ; 

 with a tegmen composed of small plates, and with a ventral tube that is 

 unusually long and transversely flattened." He states that the family is 

 distinguished from the Decadocrinidse by the continuous dichotomy instead 

 of the single bifurcation of the arms ; that their anal x, unlike that of the 

 Cyathocrinidse, is always associated with other anal plates ; that the radials 

 have a wide, slightly specialized facet ; and that their tegmen is more 

 delicate. The Dendrocrinidse are said to be represented in America in 

 the Hudson River group by Dendrocrinus, in the Devonian — both in this 

 country and in Europe — by Homoc7nnus, and in the Carboniferous by Pari- 

 socrinus, PoteriocrinuSj and ScapMocrinus. which agree in the structure of the 

 anal area ; the three latter with pinnules, the former without them. The 

 presence or absence of pinnules, and the structure of the arms, he makes the 

 leading characters for distinguishing the genera. 



He defines his second family, the Cyathocrinidge, as having " no radianal 

 or tube plate in the anal area of the dorsal cup ; with anal x either pres- 

 ent in the cup or raised above it ; with ^wq arms, simple and dichoto- 

 mous ; with tegmen rather solid." He refers to it CyathocrinuSy Gissocrinus, 

 and their descendants, with the subdivisions Cyathocrinites, Achradocrinites 

 and Codiacrinites, of which the latter have no anal at all, and some of their 

 genera have an inferradial, or a radianal, while others have not. 



