ATE. P. H. CAEPENTEE ON THE GENUS ACTINOMETEA. 109 



externally merely as small triangular pieces, not meeting laterally ; so that they exhibit 

 the same differences as the basals of Pentacrinus and of Solanocrinus. In many specimens 

 the sutures between the basals, radials, and top stem-joint are clear and distinct ; but in 

 others there is no trace of them at all, just as in some examples of JEugeniacrinus and 

 Bhizoci'inus ; but this is hardly a satisfactory reason for supposing the basals to be 

 internal and concealed, as has been done in the case of the last-named genus. 



Even in some species of Pentacrinus the basals appear to be very closely united to 

 one another, and to assume the form of an uppermost stem-segment. Thus in P. sca- 

 laris, Goldfuss 1 , there is no appearance whatever of small wedge-shaped basals, such as 

 are found in P. briareus and in P. asterla ; but, as remarked by the Messrs. Austin 2 , 

 they appear to be united into a single plate, which resembles an " enlarged columnar 

 joint." The same was probably the case in the Jurassic genus Isocrinus, described by 

 Von Meyer 3 , though it is, of course, possible that in both these cases the basals may 

 have been internal and concealed, as in Comatula. 



I have endeavoured to show elsewhere 4 that in the recent Phizocrimis we find a 

 strikingly similar case to that presented by JEugeniacrinus, viz., the sutures between the 

 basals, visible externally in one species and not in another, or, rather, not invariably in 

 another. In M. lofotcnsis the first radials rest upon a large and expanded apparently 

 simple segment, which was described by Sars 5 as the expanded uppermost stem-segment; 

 and a small circular plate situated in the central vacuity between the first radials, with 

 which, as well as with the enlarged uppermost stem-segment, it is closely connected, was 

 regarded by him as representing the metamorphosed embryonic basals of Comatula. 



Pourtales's observations 6 , as well as my own subsequent ones, have led me to believe 

 that the piece called the enlarged uppermost stem-joint of P. loftensis by Sars and 

 Ludwig 7 is composed (if not entirely, at any rate in great part) of five closely anchylosed 

 basals. Schluter s is evidently not acquainted with the evidence on which this view rests, 

 or he would scarcely suggest that B. Rawsonii might not be a Rhizocrinus at all, because 

 its basals differ from those described in P. loftensis by Sars and Ludwig ; although 

 these two observers are not themselves in accordance as to which parts of the interior 

 of the calyx are to be regarded as concealed basals. 



Sir Wyville Thomson 9 takes the same view as Pourtales and myself ; for he describes 

 how " in Rhizocrinus the funnel-shaped piece formed by the coalescence of the basals with 

 the fused first radials above and the dilated upper joint of the coalesced upper joints of 

 the stem beneath, makes up a large part of the cup ; " and his descriptions of the 

 calices of Hyocrinus and Bathycrinus, both genera allied to Rhizocrinus, together with 



1 Petref. Germ. torn. cit. p. 173, Taf. Is. fig. 10, b. 



2 'A Monograph on Kecent and Fossil Crinoidea,' p. 121 (Bristol, 1845). 



3 " Isocrinus imd Chelocrinus," Museum Senkenbcrgianum, p. 251 (Frankfurt, 1837). 



4 " Pentacrinus and Rhizocrinus," loe. cit. pp. 47-53. 5 Crinoides vivants, loc. cit. p. 4. 



6 Hassler Expedition, Joe. cit. pp. 28, 29. 



7 Rhizocrinus lofotensis, loc. cit. pp. 121, 122. 



8 0/(. cit. p. 29. Schluter was unfortunately unable to make himself acquainted with Pourtales's memoir. 



9 " Notice of new living Crinoids belonging to the Apiocrinidse," Journ. Linn. Soe. Zool. vol. xiii. p. 48. 



15* 



