370 PROCEEDINGS OF THE ACADEMY OF [1888, 



the iiiterradials extend " (p. 19), and on page 143, in our diagnosis 

 of the Crotalocrinidae, we stated : " Ambulacral furrow deep, rami- 

 fying with the arm branches, covered by alternating plates, and 

 bordered by side pieces." The ambulacra and covering pieces over 

 them, in the arms, which those figures all show, were therefore clear- 

 ly recognized by us always. 



It is worthy of note, however, that Carpenter, while pronouncing 

 us " seriously in error " in saying that there is no central piece, nor 

 proximals, nor traces of ambulacra in the figures of Angelin above 

 referred to, does not undertake to point out the presence or location 

 of either one of those elements upon the figures in question, although 

 he expresses on p. 403 his belief " that the small covering plates of 

 CrotaloGrimis rugosus are the representatives in a smaller crinoid^ 

 ' of the large rigid plates' shown in figures 6 and 7, * * * * while 

 I shall also continue to believe, until the contrary is demonstrated, 

 that the central plate and proximals are among the irregular pieces 

 occupying the oral pole in the originals of these two figures." Nei- 

 ther does he inform us that the figures themselves are totally incor- 

 rect and fanciful, although at that time fresh from an examination 

 of the type specimens at Stockholm. 



Carpenter says (oj) cit. p. 399) that " while the summit plates are 

 clear and well defined in some species and genera, there are other 

 closely allied forms, in which these plates are almost or entirely un- 

 disthiguishable among the large number of plates to be found in the 

 vault. I will only mention one instance in illustration of this state- 

 ment, viz. Cyathocrinus iowensis and C. multibrachiatus, both of 

 which are figured by Wachsmuth and Sj^ringer (Revision Part. Ill, 

 p. 65, PL IV, fig. 6, and PI. V, fig. 7), the former with, the latter 

 without any distinct summit plates. " 



These two figures, as the explanation shows, represent specimens 

 in which the summit plates were in an imperfect condition, indica- 

 ting a process of resorption or modification going on, and were 

 expressly given for the purpose of illustrating this fact. The summit 

 plates, as we stated on page 49 (Rev. Pt. Ill), " are in their arrange- 

 ment, as a rule, very regular, and only disturbed by the anal tube." 

 We stated further on the same page that the apparent disturbance 

 in some species with a large number of arms was due to a misconcep- 

 tion of the plates. It is true that in some forms the summit plates 

 are not so readily distinguished as in others, and there are some genera, 



* C. rugosus appears generally to be a much larger species than C. pulcher. 



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