CLEIOCEINUS. 95 



allied forms, we have good reason to suppose that it, like those forms, 

 possessed five small basals and three underbasals, both hidden by the 

 column. The latter were probably very minute and rudimentary, since 

 the specimen is from the • Lower Silurian, where it is almost the only 

 representative of the family. This alone induces us to try to define 

 generic characters from a single imperfect specimen. Notwithstanding, 

 therefore, that some of the elements are problematic, we propose until 

 something better is found, the following: — 



" Raised generic description. — " 



Then follows a generic diagnosis based upon the probable presence of 

 three minute or rudimentary underbasals and five basals, all hidden by 

 the column. 



In 1886 * the genus was further discussed by us, and a diagrammatic 

 figure from the type specimen, made by Mr. Walter R. Billings, was given 

 (Op. cit., PI. IX., Fig. 5), in which the hypothetical five basals and three 

 infrabasals were indicated by dotted lines — thus giving the basal structure 

 of the Ichthyocrinidae generally. A further revised generic diagnosis was 

 added, which did not differ greatly from the former one, — the chief new 

 point being that the anal plates, instead of being four or five in number, 

 extend the full length of the calyx; and that the arms are "apparently 

 recumbent." It was also stated, on information furnished by W. R. 

 Billings, that " the ridges of the column are interradial in position, which 

 confirms the supposition made by us (Part I, p. 36), that Gleiocrinus 

 possesses underbasals, and that the so-called basals of E. Billings are 

 interradials. He also states that the lowest visible circlet of plates 

 ' apparently overlaps the column, instead of passing under it,' which 

 shows that the base must have been concave, with ample space for 

 the basals and underbasals to lie concealed from view." We further 

 stated : " If certain parts were better known, we should make it the type 

 of a new family, but at present, having no positive knowledge of the 

 basal regions, nor even of the arms, we are not in a position to give a 

 satisfactory definition of the group." 



Although E. Billings had said, in his description of C. regius, that it had 

 "about forty . . . tentaculated, free rays," it was not understood that this 

 meant pinnulate arms until after the last mentioned discussion, when W. R. 

 Billings sent to Dr. Wachsmuth a drawing from another specimen of that 



* Revision, Pt. III., See. 2, pp. 152-3. 



