213 
ptesent to retain this species in the present genus. So far as its sjiecifie position is 
concerned it is unquestionably a new form. The large deltoids, and the fact of the 
radial sinuses being so largely enclosed by those plates, as well as the shallow basal 
excavations along the lines of the interradial sutures, are points of the highest 
importance. .. 
The structure of the ambulacra resembles that seen in T. oHiquatus, Eoemer. 
A little below the intersection of the sinuses by the radio-deltoid sutures, the impres- 
sions of the ambulacra on the surface of the cast abruptly cease. From these points, 
arguing by analogy, it is more than probable that they become enclosed within the 
substance of the radial plates. The surface of the cast below the visible terminations 
of the ambulacra is flattened and harpoon-head shaped, the apices representing the 
radial lips. At the proximal end of this depression are visible four hydrospire-sacs on 
each side, the outer ones becoming so much curved as to be almost at right angles to 
the ambulacra. The structure of this part of the economy of T. Carpenteri would 
seem to show that the hydrospires beneath the calyx plates w'ere not cut off from the 
oody cavity to the same extent as surmised by the late Dr. P. 11. Carpenter and the 
Writer when describing the genus generally.* A comparison with our figures t of the 
mtorior and exterior of the radial plates of T. obliquatus will fully demonstrate the point. 
This, no doubt, arises from the much greater developuieut of the deltoid plates in the 
Australian species at the expense of the radials. 
Structural details of the spiracles in Tricwlocrinus are much needed, and I 
^gret that the otherwise instructive cast now before me does not directly so assist. 
ut I believe the hydrospire canals are visible in one of the interradial areas, and 
partly so in a second. Their structure is not altogether clear, but it seems to be 
generally in accordance with that seen in the class. 
Loc. and Horizon. Eockhampton District J {Q. W. Be Vis; Colin. De Vis)— 
^ympie Beds. 
Section-ECHINOZOA. , 
Class — Echinoidea. 
Ordei-PA LECH INOI DE A. 
Family— AECHAHOCIDAEID^. 
Genus — AECIKEGIBAEIS, McCoy, 1884. 
(Syuop. Garb. Limest. Foss. Ireland, p. 173.) 
Ohs. The only evidence of the existence of this important group in the 
• ®^^oic rocks of Queensland is the occurrence of a single plate, or rather the 
^^ression of it, in Mr. De Vis’ Collection. The impression is, as usual, hexagonal, the 
surface between the latter and the central tubercle flat. The 
of tv marked. It is certainly an interambulaeral plate of a member 
jjjg family, and probably of the type genus. I believe this to be the first announee- 
^ocks occurrence of the Palechinoidea in Australian Permo-Carboniferous 
^ Zoc. and Horizon. Eockhampton District t (0. TV. Be Vis; Colin. De Vis) — 
^ympie Beds. 
* Catalogue, loc. cit., p. 205. 
t Ibid., t. 18, f. 10-13. 
t See note, page 199. 
