66 



processes are short, earshaped. The pigmentation is very sUght, with no 

 prominent spots in the point of the arms. There is a very distinct trans- 

 verse muscular band connecting the ends of the postoral and postero- 

 dorsal rods, these pairs of arms being thus actively movable, as is apparent- 

 ly the general rule in those larvse provided with a posterior transverse rod. 

 The skeleton (Fig. 24 B). The most conspicuous feature is the posterior 

 transverse rod, which ends in two branches, the lower of which carries 

 along its lower side 5—6 lancet-shaped branches, the whole structure 

 recalling a pair of antlers of a stag. The middle part of this rod may be 

 quite smooth or provided with some small processes. The posterodorsal 

 rods are fenestrated and thorny along the outer edge Uke the postoral 

 ones, only the holes are shghtly smaller. The dorsal arch has two lateral 

 processes. Both the preoral and the anterolateral rods are distinctly 

 thorny. 



Heliocidaris erythrogramma (Val.) 



PI. XVII— XVIII. 



This species, which occurs abundantly along the rocky shores of Port 

 Jackson, Sydney, was found to have ripe sexual products in February 

 ( — most probably its breeding season will prove to continue during a 

 greater part of the summer — ). The development proved to be of such 

 exceptional interest that it was thought advisable to give a preliminary 

 report of it^). The fuller record given here is also rather summary and 

 by no means complete. The preserved material is not sufficient for an 

 elaborate study of all the internal transformations; moreover, the skeleton 

 has been dissolved so that this part of the development must be entirely 

 left out, the conditions under which the larvae were reared not having 

 allowed to draw the living objects or to undertake a careful microscopical 

 study of them. Neither is it within the scope of the present work to give 

 a detailed description of the development of the internal organs and all 

 the compUcated transformations connected with the process of metamor- 

 phosis. The matter is merely indicated here. But it is evident from the 

 facts here recorded that the development of this species really deserves 

 to be made the object of a detailed monographic study, since it presents 

 so many novel and exceptionally interesting features, being upon the 

 whole, so entirely different from that of any other Echinoid hitherto 



'■) Th. Mortensen. Preliminary note on the remarliable, shortened development of an 

 Australian sea-urchin, Toxocidaris erythrogrammus. Proc. Linn. Soc. N. S. Wales XL 1915 

 p. 203—6. 



I have adopted in the present work the name Heliocidaris instead of Toxocidaris, in agree- 

 ment with H. L. Clark (Hawaiian and other Pacific Echini. The Pedinidee etc. Mem Mus 

 Comp. Zool. XXXIV. 1912. p. 281). 



