ECHINOIDEA. II. 



75 



interanibulacra (posterior series) is a little uncertain, as I was unable to see distinctl}- the limit bctweii 

 it and the ankylosed genital plate. 



There are only two genital openings, covered by long genital papillæ; it is probabh- the an- 

 terior pair whicli is fonnd, the posterior pair having disappeared, evidently becanse there is no room 

 for more than one j^air of genital organs. The madre- 

 poric pores are rather few in nnniber (PI. VI. Fig. 17), 

 placed behind the genital pores; in the specinien of 26""" 

 there are only two niadreporic pores. The genital openings 

 are present only in the two larger specimens and in a 

 separated head-end. The smaller specinien shows no trace 

 of genital openings. This species thns is not mature till a 

 rather considerable size, since a specimen of 22""" is im- 

 niature. 



The primary spines are rather scarce, only along 

 the actinal and abactinal keel they are close-set; also along 

 the anterior border they are more nnmerous; there is no 

 serial arrangement of the spines. Tlie\' are all short, the 

 longest scarcely reaching 3""" length; they are cnrved, 

 widened towards the point, which is generally bifid (PI. XI. 

 Fig. 44); they are more or less serrate, generally more on 

 one side than on the otlier. Those along the plastron 

 are somewhat more widened than the abactinal ones; those 



on the posterior end of the abactinal keel bend down over the anal area. The spines within the oral 

 invagination (PI. XI. Fig. 2i| are, as nsual, coarser and stronger than those on the ontside; they are 

 curved and more or less sharply serrate along the concave side. The miliary spines (PI. XI. Fig. 43) 

 are likewise rather scarce in number; they are only ca. 0-5""" in length, cnrved towards the point 

 which forms a somewhat widened, slightly fenestrated plate. The clavnlæ of the fasciole are somewhat 

 stronger, with a rather complicated widening at the point (PI. XI. Fig. 42). 



The tube-feet along the border of the invagination and those of the odd anterior ambulacrum 

 are rather well developed, though, of course, simple. They contain rather ninnerous irregular spicules, 

 (PI. VII. F'ig. 18) arranged in a longitudinal series. In the tip of the foot is generall)' fonnd a small 

 calcareous ring, evidently corresponding to the more developed cap (or, as it really is, ring) found in 

 Poiirtalcsia Jcffrcysi ■A.wå ir(/////f// (comp. PL VII. F'ig. 21). — The sphæridiæ are placed singly behind 

 the tube-feet along the border of the invagination. They are of the tisual shape, quite smooth, except 

 at the lower end (PI. XI. F"ig. 25). 



The pedicellariæ are represented by three kinds, viz. tridentate, rostrate and ophicephalous; no 



globiferous pedicellariæ have been found. The tridentate pedicellariæ occur in different forms, which 



are, however, connected by transitions. The smaller ones (PI. XI. Fig. 2) have a short, oval blade, finely 



serrate along the edge, except in the lower part; they differ rather mnch from those of Potirt. Jef- 



freysi etc. by the apophysis continuiug into the edge of the blade, whereas in the other species it 



10* 



Fig. 14. Apical region of Pourlalcsia paradoxa. 

 From tlie inside. 



