PALiEOCRINOIDEA. 



433 



horizontal line. Reposing directly upon the radials are the five 

 first brachials, which are as wide as the radials, but are of very 

 small vertical thickness. The arms are mas- 

 sive, moving as in one piece, uniserial, and 

 undivided. They gradually diminish towards 

 their apices, and by the accurate apposition 

 of their edges together, form a pentagonal 

 pyramid. The arm - plates bear numerous 

 small and incurved pinnules, six or more on 

 either side of each joint. These roof in the 

 deep ambulacral grooves, which seem also to 

 have had a definite calcareous skeleton of 

 their own. Between the bases of the arms, 

 in the interior of the cup, is placed a so-called 

 " consolidating apparatus," formed of five 

 laterally anchylosed calcareous pieces, which 

 apparently really represent " the united 

 muscle-plates of the radials " (P. H. Car- 

 penter). This peculiar apparatus covers the 

 greater part of the ventral surface of the 

 calyx, and the mouth appears to have been 

 placed in its centre. The column is obtusely 

 quadrangular, annulated, and traversed by a large central canal 

 surrounded by four smaller tubes. 



The only genus of this family is Cupressocrinus itself, the species 

 of which are exclusively Devonian, and appear to have been wholly 

 confined to the European area. The characters of the genus need 

 not be more fully discussed, the principal ones having been men- 

 tioned in the diagnosis of the family. 



Family n. G aster ocomi dee. — In this family the calyx (fig. 307) is 

 small and spheroidal, and is typically dicyclic, the underbasals 



Fig 306. — Side-view of the 

 cup of Citpi'essoci-iniis cras- 

 sus, with the arms folded up, 

 of the natural size. Devonian. 

 (After Schultze.) 



Fig. 307 .—Gasteroco7iia antiqua, from the Devonian rocks of the Eifel, enlarged twice, a, 

 The calyx viewed from the side ; b, The anal aspect of the calyx ; c, The ventral surface of the 

 calyx. (After Schultze — copied from Zittel.) 



being usually represented by a simple pentagonal plate. This plate 

 may, however, be merely an enlarged top stem-joint (as in Cupres- 

 socri?ms), and Zittel regards Nanocrinus as being monocyclic. There 

 are five basals, and generally an equal number of radials, with one 



VOL. I. 2 E 



