30 



STRUCTURE OF THE CYSTIDE^. 



cannot thus be seen whether the mouth was central, proboscidiform 

 or otherwise, or whether the grooves of the arms were continued 

 along the surface. 



The following three figures are taken from the Report of the 

 Geological Survey of Missouri, vol. i. part ii. plate A. Dr. Shumard, 

 the Palaeontologist of Missouri, in his descriptions of the species, 

 expressly recognizes these apertures. He says that the example of 

 A.rotund^is figured " exhibits twenty-one arm-openings." (p. 191.) 

 Of A. Verneuilianus he states " the vault consists of numerous small 

 pieces, united so as to form a nearly smooth convex surface. 

 Proboscis, sub-central. Arms, wiknown; the number of arm-openings 

 iu the specimens under examination varies from fourteen to fifteen." 

 (p. 194.) In the same plate there are figured A. Christyi (Shumard), 

 A. Misso2iricnsis (Shumard), A. pyriformis (Shumard), and A. parvus 

 (Shumard), each of which exhibits a belt of ambulacral apertures. 



Fig. 16. 



Fig. 17. 



Figure 16. Jctinocrinus rotundits (Yandell and Shumard). 

 " 17. jlctinocrinus Konincki (Siiumard). 

 " 18. jlctinocrinus Verneuilianus (Shumard). 



The above figures and remarks, if not sufficient to establish the 

 existence of these orifices, may, it is hoped, at all events indicate that 

 the subject is worthy of investigation. There are many species that 

 represented in the publications of different writers which shew that 

 there are some very interesting questions relating to the structure 

 of the ambulacra of the Crinoids yet to be worked out, and that 

 probably principles for both zoological and geological classification 

 may be drawn from this source. See the following, in Pictet'a 

 Traite de PaUontologie, Plate XCIX. :— Fig. 1. Solanocrinus costatus 

 (Goldfuss). Fig. 2. S. Jageri {GoWnss). Fig. 3. Decamerus mysticus 

 (Hagenow). Fig. 2o. Calliocrinm costatus (Hisinger). Plate C. 

 Fig. 2. Haplocrinus mespiliformis (Roemer). Fig. 3. Coccocrimis rosaceiis 

 (Miiller) ; and Fig. 7. Gasterocoma antiqua (Goldfuss). 



