42 DR. p. H. CARPENTER ON CERTAIN POINTS 



original tte type of a new genus TypM echinus *. Duncan's ob- 

 servations seem to render this unnecessary, and he was inclined to 

 attribute the apparent absence o£ radial plates in de Kouinck's 

 specimen " to crush and irregular pressure, so that the radial 

 plates were either pushed into the test or pressed away." further 

 investigations upon this point are much needed. 



If Falceeehinus sphcericus were the oldest known Urchin, wliich 

 of these conditious would Neumayr have recognized as the typical 

 one, and as representing the primitive structure of the apical 

 system, not only in the Urchins, but also in the Echinoderms 

 generally ? These considerations seem to me to tell very strongly 

 against his doctrine that this primitive type is to be found in 

 Bothriocidaris, even if we assume, which I do not, that genital 

 plates are represented in this type. If they existed, they were 

 at any rate imperforate, and it would seem, therefore, as if the 

 so-called anal opening may really have been a valvular osculum 

 common to the rectum and genital ducts, like that of the Bter- 

 asteridcs and certain Cystids. 



It is to be noted, too, that there is no distinct indication of the 

 presence of a madreporite in this genus. It is true that Schmidt 

 describes "ein System von langlichen Eurchen und Eippen " on 

 one of the five large plates at the apex of B. glolulus which he 

 identifies as the madreporite t. But he does not seem to have 

 noticed the anomaly of its position at the end of an ambulacral 

 zone ; and the plate which he thinks is of the same character in 

 B. Pahleni is similarly situated. Zittel, while mentioning the 

 presence of a madreporite, says nothing about its radial position ; 

 while Neumayr and Duncan made no reference to it in any way. 

 It is not clear, therefore, whether Neumayr believed it to be 

 ahsent in Bothriocidaris or situated in an ocular plate ; but in 

 either case the aj^plication of the same principle that he employed 

 in arriving at the primitive type of the Echinoderm apical system 

 would lead to somewhat anomalous results. U Bothriocidaris, in 

 virtue of its geological position, is to be regarded as primitive in 

 one structural feature, we must take the same view of its other 

 morphological characters ; and the conclusion is then forced u]Don 



* O-p. cit. p. 362, fig. 82 c. Neumayr described this figure somewhat inaccu- 

 rately as " Typhlechinus spharicus aus dem irischen Kohlenkalke. Nacli Baily." 

 But de Koninck gave the locality as Kirkby-Stephen in Westmoreland. 



t Loe. cit. p. 41. 



