ECHINOIDEA. II. 



75 



interambulacra (posterior series) is a little uncertain, as I was unable to see distinctly the limit betwen 

 it and the ankylosed genital plate. 



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

 terior pair which is found, the posterior pair having disappeared, evidently because there is no room 

 for more than one pair of genital organs. The madre- 

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

 placed behind the genital pores; in the specimen of 26™'" 

 there are only two madreporic pores. The genital openings 

 are present only in the two larger specimens and in a 

 separated head-end. The smaller specimen shows no trace 

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

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

 mature. 



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 numerous; there is no 

 serial arrangement of the spines. They are all short, the 

 longest scarcely reaching 3 ,nm length; they are curved, 

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

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

 one side than on the other. 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. 21) are, as usual, coarser and stronger than those on the outside; 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. o-5' n,n in length, curved towards the point 

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

 stronger, with a rather complicated widening at the point (PL 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 numerous irregular spicules, 

 (PL VII. Fig. 18) arranged in a longitudinal series. In the tip of the foot is generally found a small 

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

 Pourtalesia Jeffreysi and Wandeli (comp. PL VII. Fig. 21). -- The sphseridise are placed singly behind 

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

 at the lower end (PL XI. Fig. 25). 



The pedicellariae are represented by three kinds, viz. trideutate, rostrate and ophicephalous; no 

 globiferous pedicellariae have been found. The trideutate pedicellaria; occur in different forms, which 

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

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

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



Fig. 14. Apical region of Pourlalcsia pai-adoxa. 

 From the inside. 



