910 Transactions of the Society. 



are very different, and are apparently derived as a modification of 

 either simple bihamate or biacerate spicula. 



From each genital opening protruded a cylindrical mass of 

 generative products, apparently surrounded and held together by a 

 thin membrane. May this not be a provision favouring the passing 

 of the ova or spermatozoa beyond the long spines of this region ? 



Pedicellariae. — The gemmiform pedicellarise resemble in all 

 essential points those of EcJmiometra and Heterocentrotus. The 

 jaw terminates in a long, deeply grooved fang ; the groove, which 

 is almost converted into a canal by the meeting of its margins, 

 opening at a point near, but never at, the tip on the external or 

 distal surface. A long, solid fang rises close to the terminal one, 

 but nearer the base of the jaw, and usually on the right side. The 

 expanded, wing-like portion of the jaw is deeply notched on its 

 distal border. This character of the terminal fang, in conjunction with 

 the two glandular masses attached to each jaw, lead me to think 

 that these pedicellarise have, amongst other functions, that of intro- 

 ducing a poison into any wound they inflict. 



The gemmiform pedicellarise are of two sizes, one about two- 

 thirds that of the other. 



There is nothing remarkable about the tridactyle pedicellariaa. 

 The serrate borders of the prongs are widely separated, especially 

 near the distal extremity, which is somewhat spoon- shaped ; they 

 come in contact with one another by this part, which forms about 

 two-thirds of the entire length of the jaw. The sides of the prong 

 are pressed in forming a crest running the whole length of its outer 

 surface. 



The ophiocephalous and trifoliate pedicellarise are similar to 

 those of most Echinometradae and Echinidae. 



The ambulacral tubes have the usual bihamate spicula, but 

 much varied in size and thickness. 



Parasalenia, — This genus, which at first sight looks so like an 

 ordinary Echinometra, differs, as has been already pointed out, in 

 the arrangement of its pores, and in its anal plates — the latter 

 resembling those of Arbacia. 



Spines. — These are unlike those of any other of the Echino- 

 metradae in showing no evidence of periodicity of growth, such as is 

 met with in the rest of that family. The calcareous wedges, which 

 radiate from the interior of the spine, remaining for a long time 

 thin, and separated by a space, rather broader than themselves, 

 occupied by the usual calcareous network. Near the surface of the 

 spines, the wedges somewhat suddenly become much thickened, so 

 as nearly to come in contact. Their substance is peculiar, in 

 presenting in sections a regularly dotted character, reminding one 

 of the markings of striped muscle. They show no peculiarity under 

 polarized light. 



