52 SVEN LOVEN, ECHINOLOGICA. 



0,5 7, and 0,44, which shows that the spreading of the auri- 

 cular eircle is mnch greater in the Echinoconidee.. The anri- 

 cles and the interradial walls that connect theni, are by no 

 means as erect as in the Cidaridae or the Ectobranchiates, and 

 recline npon the test, which is more thickened, particularly in 

 the interradia. The anricles evidently arise from the ambu- 

 lacra, not, as in the Cidaridfe, from the interradia, and it may 

 be safely inferred that the ambulacral colnmns were not, as in 

 these last and in the Echinothnria;, continued to the mouth, 

 but, as in the Echinidse, had their adoral termination in the 

 peristome. The pairs of auricnlar branches do not unite at 

 the top över the ambulacrum, but while they bend towards 

 each other and their projecting ears overhang a little, they, 

 nevertheless, are widely separated. In this they agree with 

 the CidaridöB and among the Ectobranchiates with Echinocida- 

 ris and Arbacia, and to a certain degiee with Strongylocen- 

 trus, Lytechiniis, Tripneustes, Boletia, Stomopneustes, Temno- 

 plenrus, Mespilia, Amblypneustes, in which the slender an- 

 ricles feebly incline towards each other, but remain separate, 

 or little more than touch at their expanded tops; while they 

 difPer widely from the Diadematidce and Echinometridee in 

 which the branches are largely coalescing. 



The extent to wliich these peculiarities in the auricnlar 

 system of the Echinoconidse, its small dimensions, the reclining 

 position of its slender branches, in connexion with the slight de- 

 viation in the stoma from the circular form, — not consistent, 

 it seems, with a concentric homodont condition of the jaws — 

 may have been attended w^ith modifications also in the maxillary 

 apparatus, further researches will have to demonstrate. Mean- 

 while I shall here oiFer some remarks on the form of the pyramids 

 in the more normal Discoidea cylindrica, in each of two speci- 

 mens of which were found three tolerably well preserved halves, 

 and compare them with corresponding parts of Cidaris, Echi- 

 nometra and Asthenosoma. 



In the Cidaridse, as represented by the Cidaris pa])illata 

 Leske, the two halves of the pyramid are united through0,8 8 

 of their whole length, from the mouth to far above the inner 

 angles of the lateral wings, and almost to the level of the 

 tops of the supra-alveolar processes which, accordingly, are 

 separated only by a shallow notch. In the Echinometra and 

 the Asthenosoma the symphysis terminates already at 0,6 of 



