Till! A.MBULACBA. 53 



The first series of Blastoids which we received from Mr. Wachsmuth contained 

 several specimens of Oranatocrinus Norwoodi in the form of moulds of the interior of 

 the calyx (PI. VII. figs. 7-9). The boundaries of the lancet-plates and deltoids are 

 exceedingly well shown as delicate thin ridges which radiate outward from the edge 

 of the peristome, and soon fork, so as to enclose the central end of each lancet- 

 plate, or rather of the bed in which it rested. Rising from each radio-deltoid 

 suture is a kind of inverted V, which is the cast of the two hydrospire-canals thai 

 unite before they open externally by the single spiracle at the central end of each 

 deltoid. 



The original specimens from Burlington, which we received from Mr. Wachsmuth, 

 show nothing more than this ; but others, from a different locality, which have reached 

 us subsequently, are still more perfectly preserved (PI. VI. fig. 19). In most cases 

 there is a delicate acicular rod lying above the middle of the somewhat linear mould of 

 the lancet-piece. This rod is hollow in section, and enlarges very gradually towards 

 the peristome. Just before reaching the pointed central end of this linear impression, 

 it forks, and the two branches pass off right and left through the thin ridges that sepa- 

 rate the impressions of the lancet-plate and of the deltoids respectively. Eacli branch 

 meets a corresponding one from an adjacent ambulacrum, and so a pentagonal ring 

 is formed which must have lain entirely within the substance of the deltoids, or if 

 not there, immediately beneath them (PL VI. fig. 19); while the hydrospire-canals 

 converging on the spiracles were altogether above it, and their casts concealed the 

 middle points of its sides. Each of these points is slightly enlarged, and is joined by 

 delicate rods to the corresponding points in each of the two adjacent sides. The 

 result of this is to form a second and smaller pentagonal ring, inscribed within the 

 one already mentioned. The sides of this inscribed pentagon are radially situated, 

 while those of the circumscribed pentagon are interradial, and its extensions into the 

 ambulacra proceed from its angles. 



There can, we think, be no doubt whatever that the structure described above is 

 " the circular duct (oesophageal ring ■?) " which Hambach has obtained entire from a 

 well-preserved specimen of G. Norwoodi ; but we cannot agree with him in regarding 

 it as connecting a set of longitudinal ducts beneath the lancet-plate. In the first 

 place, whatever may be the case in Pentremites proper, we have never seen any trace 

 of the presence of a duct beneath the lancet-plate of Granatocrinus, of which we have 

 probably examined a greater number of species than Hambach has. Wachsmuth and 

 Springer ' figure a relatively large canal within the lancet-plate, and it also appears 

 in our own sections of the ambulacra (PL XVII. figs. 4-S). It is likewise to be 

 seen as an opening in the broken end of the lancet-plate in the partially exposed cast 

 which is represented in PL VII. fig. 9. In the other casts (PL VI. fig. 19) the whole 

 lancet-plate is removed except the part immediately surrounding this canal ; and it is 

 1 Revision of the Paloeocrinoidea, Part II. pi. six. fig. 6. 



