16 TH. MORTENSEN, ECHINOIDEA. 



There can hardty be any doubt that this form is nearly related to P. orbi- 

 cularis; but it is quite possible that it will prove to be a new speeies. To solve 

 this question definitely would require a much larger material than that at my disposal 

 and also it would necessitate a very detailed study of the whole family of the 

 Laganidae which I cannot undertake at present and to vvhich the scanty material 

 from this Expedition has no reasonable claim. 



11. Peronella tuberculata n. sp. 



Pl. IV, Figs. 10—11; Pl. V, Figs. 4, 6, 7, 11, 23, 24, 20. 



One specimen from Broome, the beach, just below low-water mark. The mea- 

 surements are as follows. 



Length 43 mm. Width 41 mm. Height 7 mm. Petaloid area 25 mm. Distance 

 from middle of periproct to posterior edge 7 mm. 



The edge of the test is slightly thickened. Oral side slightly concave. Am- 

 bulacral furrows distinct more than halfway towards the edge. Apical area slightly 

 elevated. The petals not very broad, widest in the middle, nearly closed at the 

 outer end; 51 — 54 pore pairs. The four genital pores close to the apical area. Anal 

 area naked, somewhat sunk; it is slightly transversely elongated. 



The oral side carries numerous glassy tubercles, which are very conspicuous 

 towards the thickened edge and near the peristome, where they form a short, distinct 

 radiating line in the midline of each interradius. In the middle part of the interradii they 

 are otherwise very scarce, and at the edge there are none. They are of very different 

 size; some of them are nearly twice the size of the primary tubercles, the smallest 

 only the size of the miliary tubercles. On the aboral side there are numerous small, 

 glassy tubercles along the thickened edge, but none farther up. The spines, both 

 primary and miliary, are very scarce on the oral side, except along the edge of the 

 peristome and towards the edge of the test. On the aboral side the spine covering 

 is dense as usually in these forms. The primary spines of the oral side (Pl. V, 

 Fig. 26) are 2 mm long, very slender, slightly serrate, and with a distinct, a little, 

 curved, glassy point. Those of the aboral side (Pl. V, Fig. 24) are only 0,5 mm 

 long, somewhat fusiform, without a glassy point. None of the primary spines on 

 the edge of the test are preserved, so that nothing can be said about their structure. 

 The miliary spines are 0,3 — 0,4 mm long; the point is not much widened, the margin 

 of the expanded component rods rather coarsely dentate. The radial plates of the 

 crown are not serrate in the edge (Pl. V, Fig. 23). 



The pedicellariae. A type of pedicellariae quite unique in the family of the 

 Laganidae is found in this speeies, on the oral side, namely a five-valved pedicel- 

 laria (Pl. V, Figs. 4, 6). The largest ones found are 0.3 mm (length of head) ; there is 

 no neck. The blade is slightly concave, the outer part without holes, the edge 

 irregularly serrate; the apophysis, and, upon the whole, the basal part is more or less 

 irregular. 



