KCHINOIPEA. II. 



29 



based on the true Ech. pnsillus — as is shown below — they do not give a correct representation of 

 this feature in pusillus. Tliese pores are not most numerous above the ambitus, as is stated in the 

 diagnosis of the genus Echinocyamiis given in Revision of Echini» (p. 304); on the contrary, while 

 tliey occur in a single series along each suture above the ambitus they become quite crowded on the 

 actinal side, covering a considerable part of the piates and increasing in number towards the peristome 

 (PI. XII. Fig. 27). On the analysis of the test given b\' Loven (Etudes. PI. XLI V) the distribution of 

 these small pores is ver\' carefully shown. I must add only that these pores are also found within the 

 petals, on the inner side of the double pores, though of course less numerous and diminishing in numbers 

 towards the apical s\stem, only one pore being found on the inner side of the upper pairs of pores of the 

 petals. (PI. XII. Fig. 31.) Outside the petals also a few small pores occur on both sides, but only at some few 

 of the outer pairs of pores. — In young .specimens these small pores are few in number and rather difficult 

 to see; in quite small specimens no small pores are found within the petals. — The inner edge of the 

 ambulacral piates adjoining the peristome is abrupth- bent inwards and here two considerabh' larger 

 pores are found (PI. XII. Figs. 26, 27), corresponding to two tube-feet distincth- larger than the numerous 

 small tube-feet which cover most of the actinal side. These larger tube-feet are evidenth- homologous 

 to the large buccal feet of the Regular Echini; otherwise the\- differ from the small tube-feet only in 

 size, and, like these, they are not pro\-ided with spicules or calcareous ring. 



De Meijere (op. cit. p. 107) remarks that there must be some variation in the relative size of 

 the genital and ocular pores in pKsillus^ referriug to the figures given under that name by Agassiz 

 in «Rev. of Echini. Having e.xamiued a large number of specimens of Ech. pnsillus I find that the 

 genital pores are always larger than the ocular pores, (PI. XII. Fig. 31), and that the latter are generalh' 

 much smaller, though sometimes the difference is not very great. The difference in this respect between 

 the figure 3. PI. XI. e. and figs. i and 6. PI. XIII in Rev. of Ech. is due to the faet that these figures repre- 

 sent two different species, only the former being the true Ech. pusillus. The genital pores appear \-ery 

 earh', in specimens of only c. 3""" length; I have even seen specimens of onh' 2™'" in which the geni- 

 tal openings were already distinct. — As stated b\- Loven (Etudes. PI. XVI. 139) there is onh- one 

 madreporic pore, situated uear the anterior end of the apical swstem. This feature is of some impor- 

 tance, giving a good distinguishing character between Echiuoc\<niius and \oung specimens of Clypeaster, 

 the number of madreporic pores beginning to increase early in the latter. (In a young Clypraslcr sp. 

 from vSt. Cruz of onl\- 5'"'" length I find 6 pores in the madreporic plate). 



The interual supports of the test as well as the depressions seen along the sutures between the 

 actinal ambulacral piates are rather well shown on the figures PL I. 12 — 13 of F'orbes (Monogr. Ech. Brit. 

 Tert), and PI. XXVII. 6 — 7 ofL. Agassiz. Costa also (op. cit. Fig. 2. C. D.| gives (rather coarse) figures 

 of the interior of the test. The figure given in Rev. of Ech. (PI. XIII. 7), differs very considerably 

 from those above cited; it is evidenth- another species. A detailed description of these internal struc- 

 tures need not be given, 1 may refer to the figures gi\en b\- Forbes and L. Agassiz and to the 

 one given here (PL XII. F'ig. 29) for comparison with the Ecli. graudiporus dcscribed below. It will be 

 remarked that the radiating supports continue as far as to the peristome; on the abactinal .side they only 

 continue to the outer end of the petals. Tliese ridges are formed by the edges of the interambulacra. 

 The ambulacra show, as seen from the inside, a fairly deep depression along each transverse suture, the 



