978 ME. F. A. BATHEB OJ!f UIH^TACEINUS. [DeC. 17, 



Two slabs from the same locality, collected by Mr. H. T. Martin, 

 have recently been purchased by the Trustees o£ the British 

 Museum. Since they are the only specimens of the genus in 

 England, and probably the only specimens of U. sociaUs as yet 

 received in Europe ', the description of them that Dr. Henry 

 Woodward has kindly permitted tae to draw up may interest 

 Enghsh naturalists. At the same time, the more careful investi- 

 gation that these exceedingly beautiful specimens have rendered 

 possible has enabled a few details to be more accurately filled in. 



The larger of the two slabs has an irregular area of about 

 2400 sq. cm., aud contains 23 cups, one of which shows the base 

 very clearly ; the arms are also well shown. This slab represents 

 the unweathered condition of the fossil ; the matrix is a soft, 

 calcareous yellow shale, in general aspect reminding one of the 

 Soleuhofen Lithographic Stone, but much softer and more friable. 

 According to Prof. S. Calvin^, it is composed of microscopic 

 organisms identical with those of true chalk. Where the crinoids 

 are massed together, their calcareous remains form, as described 

 by Prof. Wilhston, a dense plate. As a rule, however, the 

 separate plates and ossicles of the crinoid are far too easily 

 detached from the matrix. The calyces are flattened out, and 

 the arm-ossicles also are much compressed, ^so that their exarai- 

 natiou is not easy. This slab, registered E 6.527, is now exhibited 

 in Gallery No. 8 of the Greological Department of the British 

 Museum (iSTat. Hist.). Eor convenience of reference the cups 

 contained on it have been lettered a, I, c, &c. 



The smaller of the two slabs, with an area of 420 sq. cm., 

 contains the remains of 7 cups, of which three show the basal 

 circlet. This slab represents the weathered condition of the 

 fossil, which fact, however, rather facilitates than hinders study. 

 The shale is a pale bluish grey, and the pale yellow plates stand 

 out clearly, both in colour and relief. This slab is registered 

 E 632S, and the cups are lettered a, fi, y, &c. 



Both these slabs show a feature of fossilizatiou hitherto un- 

 noticed in Uintacrinus ; in fact, so far as I am aware, unknown 

 among crinoids. That is, the preservation of a thin layer of 

 carbonaceous material, which lines the interior of the calyx. 

 Unfortunately, the traces of microscopic structure exhibited by 

 this are of the most meagre description. 



2. MOEPHOLOGICAL DeSCEIPTIO]^ OF XJiNTACEINUS SOCIALIS. 



The crinoid consists of a crown only. There is no trace of a 

 stem, unless, indeed, the central apical plate be the diminished 

 representative of the proximal columnal, for which view there is 

 no evidence. 



^ Geh. Professor Karl von Zittel informs me, in a letter dated January 18, 

 that the Municli Museum has also acquired similar specimens. 



^ " The Niobrara Cliallc." Presidential Address, Proc. Amer. Assoc, xliii. 

 pp. 197-217 (1894) ; and in a private letter to the author, January 1896. 



