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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    of such joints as made of two, in tin's agreeing with Bather’s explanation. The specimens under examination, although one is very well preserved, do not give the faintest trace of the separate joints; yet this explanation for the presence of the additional pinnules seems to be the most rational one yet offered. Of the whole number of specimens examined, only one shows the anal tnbe mentioned by Hall. This tube is seen indistinctly in the photograph (pi. Ill, fig. 4; also text-fig. 3). The length of the tnbe is a little over half that of the crown. Horizon and locality.—Upper third of the Coeymans lime- stone at Jerusalem Hill and at North Litchfield. Cotypes in the American Museum of Natural History. Order, Atiticuuata Wachsmuth and Springer. Suborder, Xmpinnata Wachsmuth and Springer. Family, Ichthyocrinidae Wachsmuth and Springer. Genus, Ichthyocrinus Conrad. Ichthyocrinus schucherti n. sp. Plate III, figure 1 ; text-figure 4. Specific description.—Crown, including the incurved arms, an inverted, truncated cone with straight sides. Length and breadth ecpial, 19mra, the greatest breadth being at the point where the arms become free. Infrabasals not shown. Basals five, pentagonal. Badials five, hexagonal, wider than long. Costals three in each ray, wider than long, one hexagonal, the other two pen- tagonal, the upper supporting two rows of disticlials, the first three ranges of which are quadrangular and the last pentangular and followed by two rows of palmars. The palmars are of different numbers in the dif- ferent rays and even in different parts of the same ray. Two or three of the palmars are included in the cup. Each costal and each Text-figure 4.—Dia- distichal is wider than the plate of the same gram of ichthyocrinus orc]er below it, but in the palmars there is a schucherti. n . ,1 x -i • 1 decrease m the size of the successive plates. Anal area not shown. Arms free from the second or third palmar, incurved. Each row of palmars divides at least once, making the number of branches forty. Column spreading slightly at the point of union with the crown. Joints of the column thin and equal near the calyx, alternating below, the larger ones about, three times as high as the smaller. Length of column unknown.