Description of a Permian Crinoid Fauna from Texas

Abstract

The crinoid fauna here described was collected by Professor J. A. Udden in Presidio County, Texas. The specimens are all from the lower brecciated bed of the Cibolo limestone' in the east bluff of Sierra Alta creek three miles north of Shafter and one-half mile below Cibolo ranch. The fauna is of interest because it is the first prolific crinoid fauna described from the Permian of this country. The members of the fauna constitute an interesting assemblage of species, most of which belong to the family Encrinidae which is restricted in range to the late Paleozoic and the Triassic. The members of this family are characterized by the development of strong articulating ridges upon the distal faces of the radial plates and by the reduction and sometimes by the elimination of the anal plates in the dorsal cup. The only species here described which does not belong to this family is Hydreionocrinus uddeni, one of the Poteriocrinidae also having strong articular ridges on the radials, but having a full quota of anal plates and a large ventral sack. Besides the species here described there are numerous detached plates in the collection which indicate the presence of nearly as many more species, and many crinoid columns of various sizes and forms, the largest of which attain a diameter of 40mm or more. In comparing the fauna with similar faunas in other parts of the world, mention must be made of the echinoderm fauna of the upper marine series of the Permo-Carboniferous of New South Wales2 and that of the Productus limestone of the Salt Range in India.3 The species here described as Phialocrinus americanus must be compared directly with P. princeps Eth., from the Australian horizon, and,