302 CATALOGUE OF THE BLASTOIDEA-. 



which ive have not been able to again illustrate by means of the specimens now 

 before us. Thus, the form and position of the azygos basal was observed in a spe- 

 cimen in which it had been slightly thrust out of place l , and some imperfect evi- 

 dence has been obtained as to the nature of the hydrospires. We have previously 

 referred to the possibility of these being lodged partially or entirely within the sub- 

 stance of the radial plates ; and this fact is to some extent borne out by the structure 

 of a radial forming a portion 2 of the original collection of Astrocrinus Benniei, which 

 is now in the Museum of the Geological Survey of Scotland. Some folds are visible 

 on the interior of this plate, which it is highly probable are the impressions of 

 hydrospires, as shown in our figures (PL XX. figs. 4, 18, 20). Reference was also 

 made to a small spine 3 , which, although not exhibiting any traces of definite attach- 

 ment to the specimen to which it adhered, was believed to belong to A. Benniei. 

 A closer examination of the ornamenting tubercles has led us to the conclusion that 

 some of the larger ones at any rate were perforate. This fact has been indepen- 

 dently observed by our friend Mr. P. Highley whilst engaged in figuring the speci- 

 mens (PL XX. fig. 5). It is not unnatural to suppose, therefore, that the spine 

 previously referred to probably belonged to A. Benniei. This view is also supported 

 by the fact that Hambach has described Granatocrinus granulatus, Roemer, sp., as 

 possessing perforate tubercles 4 , whilst Prof. H. S. Williams and Dr. G. J. Hinde have 

 observed a similar feature in two Crinoids, Arthroacantha Ithacensis 5 , from the Upper 

 Devonian of New York State, and Hystricrinus Carpenteri, from the Middle Devonian 

 of Ontario 6 respectively. We have not had the advantage of a reexamination of the 

 detached ambulacrum 7 figured by one of us in 1876, but ample evidence was then 

 adduced to show the presence of a lancet-plate, side plates, and outer side plates. 

 The form of the calyx varies considerably, as will be evident from our figures on 

 PL XX. But the interradius opposite to the azygos ambulacrum is generally much 

 produced (PL XX. figs. 9-13), and this, as far as it goes, is one of the points of 

 difference between this species and A. tetragonus, which has the three normal inter- 

 radii tolerably equal in size (PL XX. fig. 1). Figs. 7, 8, 14, on the same plate, 

 show, however, that this is sometimes the case in A. Benniei. The relation of the 

 deltoids to the radial limbs is well seen in figs. 2, 11, 12, 14-16. 



Localities and Horizon. Midlothian and Fife; Shales above No. 1 and No. 2. 

 Limestones of the Lower Carboniferous Limestone group. (Presented by Dr. P. H. 

 Carpenter, F.R.S.) 



1 Quart, Journ. Geol. Soc. 1876, vol xxxii. t. 13. f. la. 2 Ibid. f. 14. 3 Ibid. f. 23. 



4 Trans. St. Louis Acad. Sci. 1884, vol. iv. no. 3, p. 543. We figure a fragment of tins species for the 

 purpose of showing the tubercles (PL VI. fig. 22), but we are not altogether satisfied that they show the 

 '• very distinct sockets fur the articulation of spines (?) " which are described by Hambach. 



5 " On a Crinoid with Movable Spines." Proc. American Phil. Soc. 1883, pp. 81-88. 



" "Description of a new Species of Crinoids with Articulating Spines." Ann. & Mag. Nat. Hist. 1885, 

 vol. xv. p. 157. ~> Luc. cit. t. 13. f. 17-19. 



