Vol. 54.] ME. r. A. BATHER ON" PETALOCRINUS. 403 



Fetalocrinus in Gotland (although I had fcold Mrs. Davidson of it) , 

 used the supposed resemblance of this genus to Grotalocrinus as an 

 argument for the homotaxis of the Niagara Limestone with the 

 Gotland Limestone, which he classed with the Wenlock. The 

 Gotland Limestone, however, or at least that portion of it in which 

 Grotalocrinus is abundant, is bed f of Lindstrom, and is taken by 

 that eminent palaeontologist as the equivalent of our Aymestry rather 

 than our Wenlock Limestone. Even without the occurrence of 

 Fetalocrinus itself in lower beds of the Gotland series, Mr. Weller s 

 argament could have no great force, for the resemblance to Grotalo- 

 crinus is quite superficial and does not imply ' bonds of relationship.' 

 Bat the actual facts of geological distribution at present prove no 

 more than was better established on other grounds, e. g. by Mr. 

 Weller's own description of Goniophylliim pyramidale, Hisinger, 

 mutatio secunda, Lindstrom, from the same horizon and locality as 

 P. mirahilis. In Gotland mutatio secunda occurs, according to Lind- 

 strom (1882), in marly limestone (d) above the clay : that is to say, 

 at precisely that horizon from which Fetalocrinus is as yet unknown 

 in Europe, the horizon of the Wenlock Limestone. It is right to 

 mention here that on Dec. 21st, 1895, the late Charles Wachsmuth 

 wrote to me that he had received ' an external natural mould 

 from the Niagara of Chicago ' which he referred to Grotalocrinus. 

 This was confirmed by a squeeze taken from another specimen from 

 the same beds, and kindly sent to me on Feb. 18th, 1898, by 

 Mr. Weller. The species, however, cannot be determined, so that the 

 specimens have but slight bearing on questions of synchronism. 

 Therefore, with due remembrance of the imperfect and homotaxial 

 nature of our correlation, the species of Fetalocrinus may be 

 arranged in the following geological order : — 



Silurian (Lap worth). Europe. North America. 



Upper P. expansus. 



Middle P. longus, P. mirahilis, 



Lower P. visbycensis (senior). 



„ P. visbycensis, P. angustus. 



P. inferior. 



It is probable that the publication of this paper will bring to 

 light specimens in England : search for them should be made 

 among collections, not of crinoids, but of brachiopods, especially 

 among specimens of Rhynchotreta cuneata and similar Khyncho- 

 nelloids ; some coral-fragments, as of the associated Faloeocyclus 

 joorjpita or species of Ftychojphyllum, might, if partially exposed, 

 be confused easily with an arm-fan. In fact, P. major, Weller, 

 turns out to be an Omphyma, as explained on p. 407. 



III. Desceiption of Material. 



F. mirahilis. — All the specimens are in an iron-stained siliceous 

 rock, splitting into rough slabs. This is entirely composed of the 

 remains of corals, crinoids, a few brachiopods, and bryozoa, all 

 organisms with a calcareous skeleton ; originally, therefore, the rock 



