AND ITS RELATIONS TO RECENT COMATTJL^E. 211 



therefore drops the former altogether. But he goes even further, 

 as I do also, and includes in Pentacrinus all those forms which 

 otherwise agree with the type but have no visible basals. One, 

 for example, is the P. cingulatus, Quenstedt, = Isocrinus pendulus, 

 Meyer*. Another is the Forest-Marble specimen from Farley in 

 Wiltshire, which was described by Goldfuss as P. scalaris. A 

 third is the large Chalk Pentacrinus belonging to Mr. "Willett's 

 collection, which is figured in Dixon's ' Geology of Sussex' (1878 

 edition, pi. xix. 22). Another is the P. pentagonalis personatus 

 from the Brown Jura, which is figured by Quenstedt (tab. 98. 

 fig. 137) without any notice of its peculiarities. Lastly, there 

 comes P. JFisJieri, in which basals were described by Baily f. They 

 are really, however, nothing but the first radials, the basals being 

 absent from the exterior of the calyx. It might be thought that 

 all these species without external basals should be separated from 

 Pentacrinus and placed in the genus Isocrinus, von Meyer. In 

 this way we should be making three genera out of one type, ac- 

 cording as the basals are invisible externally {Isocrinus), or form 

 an incomplete {Pentacrinus) or a complete ring {Cainocrinus). I 

 do not think, however, that such a classification would be a sound 

 one. On the same principle we should have to found a new genus 

 for Encrinus Cassianus%, in which " der perlschnurfonnige Stiel 

 deckt die tief eingesenkte Basis so stark, dass erst bei der genau- 

 esten Beinigung 5 winzige Dreiecke zum Vorschein kommen." 

 Tet another new genus would be necessary for the reception of 

 the tetramerous variety of E. liliiformis represented in tab. 107. 

 fig. 5 of the ' Encriniden.' It has no external basals at all, but 

 the radials rest directly on the top stem-joint. In the same way 

 those forms of Bourgueticrinus% in which the basal ring is incom- 

 plete, as in Pent, asteria, should be separated generically from the 

 ordinary forms with a closed basal ring. 



Seeing, then, that we have such a complete series from P. 

 Fisheri and its allies through P. asteria (PI. XI. fig. 21), P. bria- 

 reus, and P. decorus to P. Wyville-Thomsoni (PI. XI. fig. 23), 

 P. Jaegeri (PI. XI. fig. 24), and P. Sigmaringensis, a separation 

 of either of the extremes from the rest of the series seems to me 



* "Isocrinus und Chelocrinus," Museum Senckenbergianuin (Frankfurt, 1837). 



t " Description of a new Pentacrinite from the Kimmeridge \cf. Oxford] Clay 

 of Weymouth, Dorsetshire," Ann. & Mag. Nat. Hist. ser. 3, vol. vi. pp. 25-28, 

 pl.i. 



\ Encriniden, p. 472. 



§ Adlnomdra, p. 108, Trans. Linn. Soc. 2nd ser. Zoology, vol. ii. 



