The fauna of the Chazy limestone / by Percy E. Raymond.

  • Raymond, Percy Edward, 1879-1952.
Date:
[1905]
Catalogue details

Licence: In copyright

Credit: The fauna of the Chazy limestone / by Percy E. Raymond. 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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    all three divisions. This meinher is fiii-tlier marked by the appearance of the earliest of American fjryozoa, and these, unlike most Ordovician species, range throughout the entire formation above the sandstone. Division 1 is characterized by the predominance of individ- uals and species of Brachiopoda. Fourteen of the 25 species of this group occun’ing in the Chazy of the Champlain Valley are found in this lowest member, wliile only 2 of the 16 pelec- ypods are re])resented. Exactly half the species of trilobites are also found here, but specimens are not common. Gastro- pods are more numerous, as half the species are represented and individuals of some forms are abundant. They do not occur in the lower strata, but are confined almost entirely to the upper part. There are three zones in this division which are worthv of notice:— Zone I3, or the Orthis acutiplicata zone, is near the base of the division and is found at Valcour Island and Isle La Motte. The characteristic fossils are : Orthis acutiplicata^ Rafines- quina incrassata, Isotelus harrisi^ and Thaleoj)S ovata^ all long rangers except the first. Zone 1ft. The Scalites angidatus zone. The faiinule of this zone is found at Plattsl)urg and Chazy. It is located near the middle of Division 1. The characteristic fossils are : Scalites angulatus^ Raphistoma immatarum R. stamineum., Bucania sulcatina^ Camavella longirostris^ Illamus glohosus^ and Thaleops ovata. Only the first two are restricted to this horizon. Zone Ic, the Lophospira subahhreviata zone, has been found only at Chazy, but is very strongD marked. It occurs about 75 feet below the top of Division 1. The characteristic fossils are: Lophospira subahhreviata and Raphistoma stamineum., both of which are very abundant. Of less importance are the rare Schizamhon f duplicimuriatus^ Ileliomera sol, and Clionycilia marginalis sp. nov. Division %. The Maclurites magna Division.—The strata of this middle division are usually heavy bedded, dark blue and grey, fairly pure limestones, with an occasional layer of grey sparkling dolomite or of light coarse-grained limestone. The layers near the middle usually weather into nodular masses, and the fossils are frequently poorly preserved and difficult to extract. The thickness varies from 200 feet at Chazy to TOO at Valcour Island, and decreases toward the south. The char- acteristic fossils are: Maclurites magna, Rafinesquina cham- plainensis, Plmiomysplatys, P. strophomenoid€s%\). nov., Stre- p/wchetus, Eospongia varians, Eotomaria obsoletum sp. nov., Eccyliopterus fredericus, Bathyurellus minor, Ghip)humis primus, and Leperditia limatula sp. nov.