984 MR. F. A. BATHER OK UINTACRINUS. [DeC. 17, 



Schlueter (4) says (p. 58), with reference to the corresponding 



structures in U. ivestfalicus — " If one were possibly inclined to 



regard as side-arms, or indeed as pinnules, those rows of plates 



that ... lie between the arms and the arm-branches, this would 



be forbidden by the constitution of the plates, since they possess 



neither a central canal nor a ventral groove, and are united to one 



another by simple sutures." This argument, though adopted by 



Neumayr (6), is one I am unable to accept. The absence of a 



central or axial canal is nothing, since there is none in the arms of 



many Palaeozoic criuoids : it is, however, a statement that I have 



been unable to verify in U. sodalis so far as the free distal ends of 



the fixed pinnules are concerned. It is abundantly clear that the 



free ossicles in the pinnules are of the same character, and are 



united in the same way, as the ossicles of the subsequent free 



pinnules. It has also been shown that the fixation of the pinnules 



is a gradual process. There is therefore no reason to suppose that 



the fixed pinnules are anything else than pinnules whose bases 



have become partially fixed, an occurrence by no means rare in 



other genera. 



The supplementary plates are of three kinds : interbrachials, 

 interdistichals, and interpinnulars. They are all thm flat plates, 

 and vary considerably in shape and even in number. 



The interbrachials vary in number from 7 {fide B. H. Hill, 9) 

 or S {fide Clark, 8) to 12, e.g. p (fig. 7). In the specimens 

 examined by me, 10 appears to be the most usual number, e.g. 

 y, €, e (figs. 4, 5), and I have never seen fewer than 9. In each 

 interradius these plates all lie above the two adjacent radials, 

 between the fixed primibrachs and opposing fixed secundibrachs 

 1 and 2, and below the 1st and 2nd ossicles of the proximal, outer 

 or interradiad, fixed pinnules. Clark says : "The arrangement of 

 the plates does not vary ; seven in an oval band enclose the Sth, 

 or 8th and 9th, according to the number of iuterradials." This 

 may be accepted as the simplest type of arrangement ; but there is 

 considerably more variation than admitted by Clark. The only 

 stable plate is the proximal one, which rests on the upper lateral 

 margin of two adjacent radials, and abuts laterally on the two 

 IBvy Its upper margin supports the two succeeding inter- 

 brachials, but may also support the central interbrachial between 

 them. To describe the shapes and positions of all the other inter- 

 brachials would, considering their variation, be waste of tiuie. It 

 is only necessary to point out that, in the large majority of the 

 specimens before me, e. g. y, e, d, p (figs. 4, 5, 10, 7), there is a 

 single plate lying between the two proximal pinnules and the two 

 subjacent interbrachials, and separated by those two interbrachials 

 from the central interbrachial. Tliis distal plale is not shown by 

 Meek (3), or Clark, or Hill ; but it can be seen in Grinnell's (2) 

 tig. 1, although there it rests on a single interbrachial, and not on 

 two as is usual. The particular arrangement of interbrachials 

 figured by Meek and by Clark is unrepresented among the speci- 

 mens in the British Museum ; but there is no reason to doubt the 



