20r> PROCEEDINGS OF THE ACADEMY OP [1881. 



■which is profusely punctured, but evidentl}^ not by the simpler 

 ventral tube of the Sphyeroidocrinidse which is destitute of such 

 openings. Nor can we imagine that there was any such communi- 

 cation through the dome proper, its plates are perfectly con- 

 nected at their sutures, and the interradial series especially are 

 strengthened by strong braces within. 



There are evidently closer relations between Cyathocrinus and 

 Hyocrinus or genera with oral plates, than between the Penta- 

 crinidffi and Sphaeroidocrinida?, in which those plates are either 

 unrepresented or greatly modified. The latter two types form 

 the extremes, and are probably more distant in their relations 

 with each other, than most Blastoids and Cystideans from the 

 Palaeocrinoids. 



The affinities of the Palaeocrinoids with the Blastoids, become 

 more apparent by our recent discover}^ of hydrospires in a speci- 

 men of TeJeiocrinus. Their exact construction has not j^et been 

 fully ascertained, but that such organs existed in some of the 

 Actinocrinidoe is now demonstrated beyond a donbt. The speci- 

 men is fragmentary, it was obtained from a narrow cherty band of 

 the Upper Burlington Limestone, and is itself silicious. The 

 interior is solid, with the exception of a natural concavit}' beneath 

 the vault, at which point it was broken in quarrying, exposing a 

 part -of the upper face of the tubular skeleton. Portions of two 

 tubes only are visible, and these are broken transversely after 

 their second branching, the fracture giving a cross-section of the 

 tubes and surrounding parts. In Teleiocrinus as in Strotocrinus 

 proper, the lateral rim contains radiating tunnels formed by par- 

 titions between the divisions of the raj^s. The tunnels, as observed 

 by us in several specimens, are divided transversely into two com- 

 partments, of which the upper one is occupied by the ambulacral 

 tubes (PI. XIX, figs. 16 and 8). In the specimen under considera- 

 tion the lower or dorsal compartment has a semicircular outline, 

 and witliin this, below one of the branches of the ambulacral tubes, 

 there are visible two distinct folds, closely resembling the folds 

 in the hydrospires of Granatocrinus (PI. XIX, fig. 3). Beneath 

 the adjoining branch, the folds cannot be so well distinguished, 

 but the outlines of the h3'drospifes are also there faintly indicated. 

 Considering that the arms in the Blastoids are inverted and 

 recumbent, and that their calcareous portions represent not onl}' 

 he solid parts of the arms, but also a part of the test, it M'ill be 



