282 ON SOME NEW AUSTRALIAN ECHINI, 



The thoracic shield is rather longer than broad, and excavated 

 posteriorly. The last pair of thoracic limbs are about two-thirds 

 of the length of the penultimate pair, and provided with a well- 

 developed dactylos. 



The abdomen nearly equals the thorax in length ; the transverse 

 diameter of its segments is about three times the antero-posterior, 

 the former diminishing slightly posteriorly ; the abdominal 

 segments (as also the last segment of the thorax) have each, as 

 in Ibacus, a mesial dorsal carina ending on the posterior border 

 in a small conical tooth ; the pleura are very prominent, and 

 resemble those of the adult ; but they are more strongly curved 

 backwards ; those of the penultimate segment have two triangular 

 teeth (represented in Ibacus PeroniiJ on their posterior border. 

 The abdominal appendages have both rami slender and tapering ; 

 the endopodite has a small, tooth-like internal process. The form 

 of the telson agrees precisely with that of the corresponding 

 structure in Ibacus Peronii. 



It is not unlikely tli«t the Phyllosoma Duperreyi of Guerin, 

 f Voyage de Dv/perrey, Zool., t. II., p. 2, p. 46 ; pi. 5, fig. 2 ; Mag. 

 cVJEnt., 1830, 4 me. livraison, pi. 12), which, like the present form 

 was obtained in Port Jackson, may be an earlier stage in the 

 development of the same animal — the antenna) and abdomen 

 being less highly specialised. 



On some new Australian Echini. 



By the Eev. J. E. Tenison- Woods, F.L.S., F.G.S., &c, Pres. 



Lin. Soc, N.S.W. 



[Plates XIII.-XIY.] 



The following species were collected between Port Jackson and 

 Moreton Bay. They are new and extremely interesting, but the 

 observations I have to make on each I will reserve for the end 



