128 



In the foregoing pages the ambulacral apertures of the Cystidea and 

 Blastoidea are treated of, as having been entirely reproductive in their 

 function. This view, however, can only be correct, in so far as regards 

 those genera that have calycine pores or hydrospires. There are some 

 that have no poriferous structures in the test or body-wall, and to such 

 the rule does not apply. For example :— in fig. 85 the two apertures of the 

 Cystidean Malocystites Murcliisoiii are given, natural 



size, drawn from a specimen in which they are very per- 

 fectly preserved. I believe that the larger of these two 

 openings is the mouth and anu? combined. The smaller 

 is the ambulacral aperture. The body-wall is totally 

 Fig. 85. non-poriferous, and, consequently, it could not have been 

 respiratory. If this species possessed any external respiratory organs at 

 all (such as those that are situated in the grooves of the arms and pin- 

 nules of the existing Crinoids) they must have communicated with the 

 interior, through this smaller aperture. Whatever, therefore, may have 

 been its other functions it must have been, at least in part, a respiratory 

 orifice. There are two grooves issuing from it. Each of these divides 

 into four or five branches, which radiate over the surface of the test, and 

 extend down the sides, in some specimens, nearly to the base. If the 

 ovaries were situated in the pinnules, and if there were any connection 

 between them and the interior, that connection mast have been made by 

 the agency of one or more organs passing through this same smaller 

 orifice- Assuming this to be true, then this opening was both respiratory 

 and reproductive. It should not therefore be called the ovarian " but 

 the " ambulacral aperture "as it was originally designated in my decade 

 No. 3. 



The above relates, only to those Cystideans which have not pores or 

 hydrospires in the test or bo.ly-wall. With regard to those that have 

 pores, such as the SphcBronites , or those that have hydrospires {Glyp- 

 tocystites, Sc.) there may have been two kinds of respiratory organs. 

 1. The pores or hydrospires. 



2> The ambulacral canals, in the grooves of the arms. 

 Granting that this was the case, then these latter could only commu^ 

 nicate with the interior through the smaller apical aperture (Fig. 85.) 

 This orifice would, therefore, be both respiratory and reproductive, as it 

 probably was in Malocystites. It should be called, simply, the ambu^ 

 lacral aperture." 



