(XT I .All AND <; i:\ITAI, IM.ATKS. 



00 



of species that typically have all oculars exsert. In three speeimens (0.4%) ocular V alone 

 is just insert (text-fig. 63) and in one specimen ocular I alone i- insert <te\t-fig. 04), a condi- 

 tion seen often as a first stage of incoming of oculars in development ; but :i> V insert is a 

 frequent variant in the order, probably it typically comes in first in tl.i- -peei.->. In 3% ocular* 

 V, I are insert (text-fig. 65). These are all arrested variants. As progressive variant- instead 

 of the typical three plates, oculars V, I, IV, II arc insert ins', irxt-fig. 67). Tlii- i> .if interest 

 as these plates are the bivium and posterior pair of the trivium marking the bilateral -ymmetry 

 of regular Echini. In 4% oculars V, I, IV, III are insert (text-fig. 69). This arrangement of 

 four plates is relatively rare in E, tribuloides while it is a common variant in Citlnri* affmu 

 as there discussed. In 25 % all oculars are insert (text-fig. 68). This is the ext n-me pn>nn ive 

 variant of tribuloides, and is comparable to the typical character of Phyllacunthu* baculota 

 (text-fig. 169, p. 149), or other species in which typically all oculars are insert. In only two 

 specimens out of the 849 examined was the arrangement aberrant. In these variants one has 

 oculars I, IV, III insert, V, II exsert; the other has oculars V, IV, III insert .1.11 exsert. Both 

 are sporadic variants and evidently cases of incomplete V, I, IV, III insert. In studying the 

 specimens they were tabulated in lots of one hundred each, and it is worth noting that the 

 percentage of the typical arrangement and the variations came out in each lot with hardly 

 any difference, and the same regularity occurred in most species studied. 



In Goniocidaris nutrix (text-fig. 72), typically (86%) the oculars are all fully exsert and 

 a ring surrounds each ocular pore. This ring is a striking character not existent in Goniocidaris 



1 



V 



TEXT-FIGS..72-74. Ocular plate arrangement in C'ularidae. 



72. Goniocidaris nutrix (Wyville Thomson). Kerguelcn Island, Antarctic. Dial... '-'7 ....... 



X 4. All oculars exsert, elevated ring around ocular pores, genital pores huge. 



73. Goniocidaris canalicvlala A. Agassiz. Falkland Island*. Di:u,,. -' t mm. R. T. J. Coll.. 7 1 1 

 insert (compare with young, Plate 2, fig. 3). 



74. The same. Falkland Islands. Dial... 22 mm. H. T. J. Coll., 71-V 

 reaching beyond plates. 



