UINTACRINUS: ITS STRUCTURE AND RELATIONS. 39 



away the plates." Bather, with the British Museum material, was equally 



unsuccessful.* 



Hill's reasons for not expecting to find any of the ventral plates are not 

 good. There is nothing in the globose form or heavy arms to prevent the 

 preservation of the disk, any more than in any other form or style of arms. 

 That which did render its discovery improbable was the pliant test, which 

 was always crushed more or less flat. On this account the only chance was 

 to find a case where the Crinoid had settled down into the soft ooze with its 

 arms outstretched and ventral side down, so that it should be flattened ver- 

 tically instead of transversely, and the disk at the same time be pressed into 

 the plastic matrix. For these I kept a sharp lookout while taking out the 

 specimens at Locality No. 1. In several specimens where the arms or calyx 

 plates were broken off, I soon discovered the existence of a large, funnel- 

 shaped anal tube, which was unknown before. Some specimens were found 

 from time to time in the desired position for exposing the disk, but most of 

 them proved a disappointment, as the disk was destroyed, and only the 

 large calyx plates showed through. Finally, however, some such specimens 

 appeared in that part of the layer where the preservation was the best, 

 having the ventral side deeply covered with a firm and exceedingly fine- 

 grained bluish chalk, or calcareous mud. On removing this with fine tools 

 and brushing, I came to a jet black surface, which seemed to be the remains 

 of a carbonaceous integument, studded with small, irregular calcareous 

 granules, of lighter color. It was so frail, thin, and brittle, that parts of it 

 scaled off with the least touch, and the first specimen exposed gave but 

 little idea of the nature of the disk, and no hint at all of the remarkable 

 facts afterwards disclosed. The other specimens were left for future clean- 

 ing, when by the exercise of the greatest care, and the most delicate 

 manipulation, mostly under a magnifier, I was rewarded by the exposure of 

 a perfect disk, which exhibited, to my astonishment, a ceniral anal p-otuher- 

 ancc, and viarginal month, — a type hitherto unknown among Crinoids, recent 

 or fossil, with the exception of the Coinatulid genus Actinometra, and per- 

 haps the Triassic Holocrinus. Several others were afterwards developed, 

 which brouirht out various details in such a manner, that the form and 

 structure'of this portion of the Crinoid could be studied almost as well as in 

 specimens dredged from the ocean. The preservation is most beautiful; 



* Proc. Zool. Soc. Loudon, 1S95, p. 979. 



