

SPECIAL CHARACTERS OK (iMMTAJ, IM.ATKS. 



171 



pundulata (text-figs. 197, 198), in which I previously described them Mai-Urn. Is'.Mt, p. |.;n 

 Similar extra genital pores have been seen in Kurltlnrix ////////,/,*, />////,</.* affini* (text-fig. I i:, 

 Strongylocentrotus fmnciscanus (text-fig. 199), ,S'. ,/ro/,,,,-/,/,,,.s/.s (text-fig. !,. ;ill ,l i,, : ,i,y ..th.-r 

 species. In S. drobachiensis extra pores were -ecu in ISO specimen-.. Dr. .M,,ri"M-i-n v. 

 me that such extra pores are connected with the genital glands. They are alua\- 



TEXT-FIGS. 197-199. Extra pores in genital plates. 



197. Arbacia punctulata (Lamarck). Woods Hole, Massachusetts. Diam. :!I nun. It. T. J. Coll., 056. X 3. All 

 oculars exsert. 



198. The same. Diam. 35 mm. II. T. J. Coll., 655. X 3. Ocular V insert (p. 1 15). 



199. Strongylocentrolus franciscanus A. Agassiz. California. Diam. 123 mm. K. T. J. Coll., 726. X 2. Oculara 1, 

 V insert (compare text-fig. 115, p. 117). 



and apparently may be considered a parallel variation to, rather than a genetic connection with, 

 the Palaeozoic types where extra pores typically occur. 



In the Ordovician Bothriocidaris (Plate 1, fig. 2) genital pores are unknown; it may Ix- 

 that they were wanting, as such pores are wanting in young Echini. More likely they e\i>tel 

 but do not show in external view, as noted in Salenia pattersoni (p. 112). In an ancient fossil it 

 would be easy for small genital and madreporic pores to be so filled up as not to be recognizable, 

 for frequently in fossils pores cannot be seen when we know from other specimens that such 

 existed. In Lepidechinus (Plate 63, figs. 7, 8) there is one pore in each genital plate in tin- 

 only species of the genus in which the apical disc is known. 



In other Palaeozoic Echini genital plates typically have more than one pore \ ;\ plate. 

 There may be two or three, as in Lepidesthes (Plate 68, fig. 5), or there may be three to live 

 in a plate, as in Palaeechinus (Plate 29, fig. 6; Plate 30, fig. 4), Lovenechimis i Plate 11, fig. 3), 

 and Melonechinus (Plate 56, fig. 6). Instead of a few pores there may be numeruu- genital 

 pores to a plate, even as many as ten or eleven, as shown in Lepidooentnu (Plate 21, fi- 

 Pholidechinus (Plate 28, fig. 10), and Perischocidaris (Plate 67, fig. 3). It is possible that in 

 types where fine madreporic pores are unknown, some of the larger pores served as madreporic 



