286 Bihliographical Notices. 



radial or a radial position, and Heterocrinus has been described by 

 Hall, Meek, and others as having a " pentapartite " column. 



Having discovered what appear to be almost invariable rules for 

 determining the presence or absence of underbasals in a Palaeocrinoid, 

 the authors turned their attention to the Neocrinoidea, with the 

 following result (p. 8) : — " Among Neocrinoidea our investigations 

 could be extended only to comparatively few genera, as unfortu- 

 nately these forms have either a round column or a circular canal. 

 Only in a few species of Pentacrinus, Millerocrinus* , and A2nocrinus 

 did we succeed in making oiif one or the other of these points. In 

 these genera, underbasals are said to be absent, but, cmiously enough, 

 the outer angles of the column are interradial, the cirrhi and radia- 

 tion along the axial canal radial, exactly as in the column of Palseo- 

 crinoidea with underbasals, and, what is more remarkable, as in 

 Extracrinus, in which, on the contrary, underbasals are said to be 

 present. The latter seems to suggest that probably many Neocri- 

 noidea eithe':' possess small underbasals or these were present in 

 their larval form." On p. 71 it is positively asserted that Neocri- 

 noids " are built upon the plan of dicyclic Crinoids. The angles of 

 the column are directed interradiaUy, the cirrhi radially." 



Let us see how far these remarks are justified by facts. In the 

 first place, there are no' cirri at all upon the stem in two out of the 

 three genera which are mentioned bj^ the authors on p. 8 ; and it 

 would therefore have been better if they had said with respect to 

 these three gerera that the cirri are radial " when present." 



A long series of plates illustrating the structure of these two 

 genera {Ajiiocrinus and Miller icvinns), which have no cirri on the 

 stem, is given by Mons. de Loriol in the work on the French Jurassic 

 Crinoids which we have noticed above ; and as Messrs. Wachsmuth 

 and Springer have copied two of the figures which it contaijis, Ave 

 may fairly conclude i^hat they have studied it with some care. We 

 have examined it for the purpose of testing their statements, and 

 have been surprised to find that in eve^y species of A-piocrinus 

 which has pentagonal upperirost sten" -joints the angles are 

 directed radially ; and j-et it is one of the three genera of which 

 "Wachsmuth and Springer state that " curiously enough the outer 

 angles of the column are interradial," as in dicyclic Crinoids. In 

 the case of Ilillericrhius the angles of the stem are radial in about 

 half the species, just as in Apiocrinus ; while they ai'e interradial in 

 the other half, which includes the two species in which underbasals 

 are figured and described by de Loriol. This latter point therefore 

 teUs in favour of the authors" theory, as also does the fact that 

 Extracrinus has underbasals and a column with interradial angles 

 and radial cirri. But it is clear, on the other hand, that their very 

 positive statement on p. 71 will need some considerable qualification 

 before it can be applied to all the Neocrinoids. 



The genus Pentacrimis presents difficulties of precisely the same 

 kind. Although it has no underbasals the angles of its stem are 



* This is generally spelt Milkricrinus by students of the Neocrinoidea. 



