TJINTACRINUS : ITS STRUCTURE AND RELATIONS. 53 



ological, not morphological. Of like secondary and non-essential nature 

 he considers the thinness of the test (although on p. 1000 he says that 

 the thickness of the cup-plates of Apiocrimts forbids us to infer any direct 

 affinity with Uintacrinus), the large size of the calycal cavity, the flexi- 

 bility of both test and arms, in which these forms have come to resemble 

 one another. Tlie essential dissimilarity, by which the secondary character 

 of the foregoing resemblances is made more apparent, he considei's to be 

 that while " 3Iarsupites has radials, basals, and infrabasals, Uintacrinus has no 

 infrabasals, but in addition to its basals and radials, has brachials, inter- 

 brachials ... all helping to compose its dorsal cup." 



Without disputing the contention that the characters thus considered as 

 secondary may be due solely to environment, I wish to point out that the 

 reasoning based upon the assumed " essential characters " of Uiniacrimis 

 loses some of its force when it is discovered that in one of those essentials — 

 the one to which Mr. Bather attaches the greatest importance — the calyx 

 of Marsupites and that of one form of Uintacrinus, from the radials down, are 

 identical ; that for this reason the morphological dissimilarity between Mar- 

 supites and Uintacrinus is not so complete as it before appeared; and that 

 the derivation of Uintacrinus from any given form cannot now be predicated 

 upon the possession of " 5 basals and 5 radials," which were considered 

 among the essentials of structure pertaining to Uintacrinus. It must also 

 be noted,, though Mr. Bather did not base any argument upon this point, 

 that Uintacrinus cannot now be considered as a pseudoinonocyclic form, in 

 the sense that the centrale might be the fused infrabasals ; for, as already 

 shown, the two forms of Uintacrinus are either distinctly monocyclic or dis- 

 tinctly dicyclic. I do not wish to be understood as contending that Mar- 

 supites and Uiniacrimis are closely related, — on the contrary, I consider 

 them widely different, and I agree with Bather that Carpenter's and Nichol- 

 son's reference of them to one family was erroneous. While Marsiqntes has, 

 from the radials down, the calycal structure of the dicyclic Uintacrinus, the 

 two really belong to totally different types. Marsupites is an Inadunate 

 Crinoid. Its brachials, though sometimes loosely united by small plates, 

 are not incorporated into the dorsal cup; its radial facets are very narrow, 

 not occupying half the margin of the plate, tlius making the arms perfectly 

 distinct from tlie dorsal cup. Uintacrinus is not an Inadunate Crinoid ; but 

 on the contrary it has brachials and pinnules deeply incorporated into the 

 dorsal cup by means of an interbrachial system on a par with that of the 



