INVERTEBRATES. 271 



possibly the exception of the last one (T. nobilis), evidently belong to the genus 

 as restricted by those who admit the genus Forbesiocrinus. 



As McCoy, however, who first followed Phillips in the use of the generic 

 name Taxocrinus (Garb. Foss. Ireland, p. 178 — 1844), evidently viewed T. 

 macrodactylus, Phillips, as the typical form of the genus, it would, according to 

 the most generally accepted rules of Naturalists, become the type of the genus 

 for all time to come, though it would have made no difference had he regarded 

 any of the others, with possibly the exoeption of the species nobilis, as the 

 type, as they are all true Taxocrinus. At the same time, McCoy also included 

 another species (T. polydactylus), which, according to his figures and descrip- 

 tion, appears to have neither anal nor interradial pieces, though it is quite 

 probable it sometimes has one of each. McCoy at that time, however, descri- 

 bed the genus as if having five basal pieces directly alternating with five 

 radial series, and the latter forming free arms, without interradial or anal 

 pieces ; at least he mentions neither of the latter. But in redescribing this 

 genus in 1851, according to the later improved nomenclature of the parts 

 (Brit. Pal. Foss., p. 53), he distinctly states that it has "five hexagonal inter- 

 radial plates intervening between the second primary radials, resting on the 

 upper lateral edges of the first do ;" meaning, as is evident from his specific 

 descriptions, one plate to the anal, a,nd one to each interradial space. 



The genus Forbesiocrinus, proposed by de Koninck and Lehon, in 1854 

 (Rech. Grinoides, p. 18), was founded upon their F. nobilis, suspected by them, 

 as above stated, to be the same as Taxocrinus nobilis, Phillips. In their descrip- 

 tion of Forbesiocrinus, these authors characterize it as having five basal pieces, 

 directly alternating with five series of primary radials, consisting of four pieces 

 each, with the anal and interradial spaces each occupied by from 12 to 13 pieces, 

 and the axillary spaces by three small pieces each. 



From all the descriptions and illus.trations-yet published, of the groups Tax- 

 ocrinus and Forbesiocrinus, it is therefore clearly evident that these two types 

 as understood by European authors, are distinguished by Taxocrinus having 

 but one or two ranges of interradial pieces, or none, and Forbesiocrinus, from 

 twelve to thirteen of these pieces occupying each interradial space, and a 

 few small pieces in the axillary spaces above. In all other points of structure, 

 and arrangement of parts, whether of the column, basal, radial or arm pieces, 

 they are understood and acknowledged to agree exactly. But as it has been 

 found that typical species of Forbesiocrinus, possess three more or less developed 

 basal pieces within or beneath those regarded as such by de Koninck and Lehon 

 (Iowa Report, p. 628), it might be supposed this character would aid in distin- 

 guishing the two groups. It is well known, however, that American typical 

 species of Taxocrinus, without interradial or anal pieces, or with but a single 

 range of the two, such as T. Theimei and T.juvenis=(Fo7-besiocrinus Theimei 



