NOTES ON EOHINODERM MORPHOLOCxT. 



17 



paper/ wliich is unfortunate; for I think it might have led 

 him to reconsider his statements. It is there pointed out that 

 the Ophiurid may be compared to a dicyclic Crinoid without 

 the necessity of regarding the radial primaries as under-basals, 

 and the mouth-shields as parabasals, or basals proper. Studer 

 does not appear to adopt the views of Ludwig and myself 

 respecting the homology of these mouth-shields with the orals 

 of Crinoids. For though he calls them " parabasals" he also 

 gives this name to the primary interradial plates which support 

 the orals of Coccocrinus. As I have already pointed out, 

 these are above the radials instead of below them, as they 

 should be if they are to ^represent the parabasals of true 

 dicyclic Crinoids such as Poteriocrinus. They are not 

 called parabasals by Zittel, whom Studer quotes, nor by 

 Schultze; and I cannot make out that any other palaeonto- 

 logist has ever spoken of them by this name. In every Crinoid 

 with a dicyclic base the upper row of plates rests directly upon 

 the lower. Whereas in Coccocrinus, the type selected by 

 Studer, the so called parabasals are separated from the basals 

 by the ring of primary radials. It is only by employing this 

 novel terminology that Studer is able to carry out his com- 

 parison between the Crinoid and Ophiurid; while the position 

 which he assumes, intermediate between those of Ludwig and 

 myself, is a very singular one. He adopts Ludwig's view 

 respecting the homology between the mouth-shields of 

 Ophiurids and the genitals of an Urchin, on account of the 

 " dorsal origin " of the former and their relation to the water- 

 vascular and blood-vascular systems ; but he agrees with me 

 in comparing the parabasals of dicyclic Crinoids ^ and the 

 basals ofPentacrinus to these same genital plates in the 

 Urchins, and the first formed interradials in the young Starfish. 

 Consequently the parabasals of the dicyclic Crinoids represent 

 the mouth-shields of Ophiurids. It is this conclusion which 

 he reaches (verbally) in his reasoning on Coccocrinus, where, 



1 This Jouraal, vol. xxii, October, 1882, pp. 378—381. 

 ' I presume that Studer is here referring to true dicyclic Crinoids like 

 Poteriocrinus and Marsupites, and not to Coccocrinus. 



VOL. XXIV.— -NEW SER. B 



