112 Messrs. Austins' Arrangement of the Crinoidea. 



of cirrhi, aided by the contraction and extension of the animal's body. 

 The tentaculated mouth forms a prominent feature in its organiza- 

 tion. 



Class 6. Vermistella, Aust. MS. Vermigrada, Forbes. 



The cirrhi, which constitute in part the organs of motion in the 

 fifth class, are wholly wanting in this; the alternate contraction 

 and extension of the animal's body alone effecting progression. 



It will be seen on reference to the foregoing arrangement 

 of the Crinoidea that several genera and species have been 

 suppressed or unacknowledged. This has not been done with- 

 out due consideration, but as it would extend this paper, al- 

 ready too long, to an unreasonable length to discuss all the 

 facts which have led to the proposed alteration, we shall 

 merely observe, that some writers on the Crinoidea have found- 

 ed genera and species on imperfect evidence, such as minute 

 fragments of columns, seldom to be relied on, while others 

 have taken the shape, into which the particular specimen they 

 described from may have been squeezed into or contorted by 

 violence at its death, or during its subsequent entombment in 

 the strata, as the data on which to found generic and specific 

 distinctions. If such evidence as this is to be admitted as le- 

 gitimate grounds to proceed on, we could undertake to double 

 the number of species heretofore described without going be- 

 yond the limits of our own cabinet for specimens. Others, in 

 their anxiety to correct the errors of preceding writers, have 

 sometimes fallen into mistakes of equal importance when re- 

 founding genera. When this has been clearly the case, we 

 have retained the original name whenever it could be done 

 with propriety. In other cases we have retained the specific 

 name only as given by the founder of the species. 



Several unnoted genera and many species are still under 

 consideration. 



Among the varied forms observable in the Crinoidea, we can 

 trace them step by step as it were merging from their ancient 

 prototypes to their existing analogues of the recent seas. The 

 genus Echinocrinus, founded by Professor Agassiz, is not the 

 least remarkable among these forms as the precursors of the 

 Echinites. Another genus [Astracrinites of our MS.) offers 

 so many affinities to the recent and fossil Echinodermata, that 

 we consider it the most remarkable of all the known genera. 

 By its being lobed it approaches to the Lobistella ; its ambu- 

 lacra, spines and anus mark it as allied to the Echinites, while 

 the arrangement of its calcareous plates connect it with the 

 Lilies of the ocean. In short it possesses the lobes of a star- 

 fish, the ambulacra and spines of a sea-urchin, and the plates 



