Revision of the New York Helderbergian crinoids / by Mignon Talbot.

  • Talbot, Mignon.
Date:
[1905]
Catalogue details

Licence: In copyright

Credit: Revision of the New York Helderbergian crinoids / by Mignon Talbot. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    crimes scopcerius is said to range from the Manlius almost to the top of the Coeymans. Most of the specimens in the Yale collection were found about forty-six feet from the top of the section in a twelve-inch layer containing slabs rich in Ilomo- crimes scoparius and also specimens of Melocrinus pachydac- tylus, Anomalocystites cornutus, Lejpocrinites gebhardi and the ophiuroids. Cordylberimes plumosus is abundant in the lower bed mentioned later. The collection from North Litchfield is chiefly from two horizons and is extremely rich. One of these beds is a lime- stone four inches thick in which are specimens of Melocrinus nobilissiim.es with very large crowns and very stout, long stems and a large form of Cordylocrinus jplumosus in comparative abundance, tlie majority of the individuals showing many long cirri crowding around the calyx. The material from this zone has one specimen of Lepocrinites gebliardi and several of Homocrinus scopariies. Although all the fossils in this bed are of large size, especially is this true of Melocrinus nobilis- simus, whose columns are very thick and, though only frag- ments, measure from fifty to seventy centimeters- in length. This is long for Paleozoic crinoids. Wachsmuth and Springer state that no columns over three feet in length have been seen from the Paleozoic and that generally they are not over one foot long.* Here there are numbers over two feet in length. The other horizon, a few inches higher in the section, has furnished slabs covering a floor space of some sixty-five square feet, slabs that are literally covered with crinoid stems and crowns. Here, too, as in the lower bed, are stems over two feet long. The forms represented are Mariacrimes beecheri, Melocrinus nobilissimus, M. pacliydactyh.es, Thysanocrinus arborescens and Cordylocrinus plumosus. To show the rela- tive abundance of these species, an enumeration of the indivi- duals on the slabs was taken and by actual count there were found, of Mariacrinus beecheri thirty-one specimens, of Melo- crimes nobilissimus six, of M. jxechydactylies one, of Thysano- crinus arborescens ten, and of Cordylocrinus plumosus eight hundred and seventy-three, making a total of nine hundred and twenty-one specimens. In addition to these are numerous crinoid columns, several gastropods and brachiopods and one cephalopod. On a small surface of six square feet there are three hundred and twenty crinoids. The cover of this bed is also in the collection and it is esti- mated that two-thirds as many more crinoids are on its lower surface. This enumeration was made before anything was •J U done toward developing the slabs and such preparation may * North American Crinoklea Camerata, vol. i, p. 39; Mem. Mus. Comp. Zool., Harvard College, vol. xx, Cambridge, Mass., May, 1897.
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