S. W. Williston — Restoration of Limnoscelis. 457 



Art. XL. — Restoration of Limnoscelis, a Cotylosaur Rep- 

 tile from New Mexico ; by S. W. Williston. 



A description of the skeletal structure of Limnoscelis 

 paludis Will., based upon two specimens in the Yale Museum, 

 has been given by me in the papers cited below.* 



Since the time of my studies of these specimens they 

 have been thoroughly and carefully divested of their conceal- 

 ing matrix without destroying the relations of the different 

 parts. Ail additional specimen of the same collections, con- 

 sisting of pelvis, femora and tail, has also been detected and 

 prepared. A fourth specimen of the same form, of somewhat 

 smaller size, but in excellent condition so far as it goes, col- 

 lected by myself in New Mexico, has also been of service. 

 From a careful study of all this material, as now prepared, I 

 am able to determine some additional facts in the osteology of 

 this remarkable reptile, and to make a few corrections of my 

 previous papers. 



In the restoration given herewith (fig. 32, p. 467), the skele- 

 ton as far as the base of the tail has been drawn almost exclu- 

 sively from the more perfect holotype specimen (No. 811, 

 Yale University). As has been stated, the relations of the 

 bones of this specimen had been disturbed but little in fossili- 

 zation, except for a part of the tail. Of the tail, the parts pre- 

 served are the proximal vertebrae in position, but with the 

 spines somewhat injured ; and a nearly continuous series of 

 twenty distal vertebrae. Of specimen No. 809, Yale Uni- 

 versity, the skull is missing, but the hind feet are in better 

 preservation than those of the holotype ; of the tail, twenty- 

 three vertebras are preserved in articulation with the sacrum, 

 and eighteen distal ones are preserved in several series. Speci- 

 men .No. 819 (Y. U.) comprises a fragmentary pelvis and 

 incomplete femora, together with the nearly complete tail in 

 natural articulation in the matrix, as shown in figs. 24-26. 

 The caudal vertebras are in two series ; the first, beginning 

 with the fourth (fig. 25), extends to the thirty-third ; the 

 second (tig. 25) comprises twelve vertebrae, with which several 

 terminal ones were found associated in the matrix, but sepa- 

 rated. Between the first and second of these series, the size 

 indicates a loss of three or four vertebras, as indicated by the 

 uniform shading of the restoration. From the tip of the tail 

 at least eight or ten are missing, making a total of about sixty, 

 of which forty-eight are actually present in specimen 819, 



* This Journal, xxxi, 380, May 1911 ; American Permian Vertebrates, p. 

 23, Oct. 1911. 



