THE SKELETON OF TRIMERORHACHIS 



S. W. WILLISTON 



University of Chicago 



A year ago, in a paper on the structure and habits of Tri- 

 merorhachis, I said, that "it will only be by the fortunate discovery 

 of a connected skeleton that the tail, ribs, and feet will be made 

 known." 1 Such a specimen has been discovered and skilfully 

 worked out by Mr. Paul Miller, a photograph of which, as pre- 

 pared, is shown in Fig. i. The specimen came from the pale- 

 ontologically famous Craddock Ranch, near the town of Seymour, 

 Texas, from the same horizon as that of the skeleton of Seymouria, 

 described by me a few years ago, and within a stone's throw of its 

 locality. Its horizon seems to be nearly the same as that of the 

 Craddock bone-bed, from which so many remarkable specimens 

 have come. When found, the specimen was inclosed in a large, 

 irregular nodule of bright red claystone; nothing was visible of 

 it except the extreme tip of the nose and the base of the tail, as 

 shown by a fracture. The under side of the nodule was smoothly 

 convex both longitudinally and transversely; its upper side was 

 irregular and gnarly. With this specimen, and in immediate rela- 

 tion with it as it lay upon the surface, were found a number of 

 pieces, which, when fitted together, formed a block about one foot 

 in length, which seemed to be a continuation of the tail end of the 

 larger block. When fully prepared, however, the smaller block 

 proved to belong to a second specimen of Trimerorhachis , includ- 

 ing about twenty chiefly precaudal vertebrae, with their ribs and 

 an imperfect femur. 



The larger specimen, that figured herewith, is a nearly complete 

 skeleton as far back as the sixth or seventh caudal vertebra. The 



1 Cope, Proc. Amer. Phil. Soc, XVII (1878), 524; XIX (1880), 54; Amer. Nat- 

 uralist, XVIII (1884), 32; Case, Revision of Amphibia and Pisces of North America 

 (ion), 39, 106; Huene, Bull. Amer. Mus. Nat. Hist., XXXII (1913), 372; Broom, 

 Anatom.Anzeiger, XLV (1913), 73; Bulletin Amer. Museum, XLV (1913); Williston, 

 Journal of Geology, XXI (1913), 625; XXII (1914), 160; XXIII (1915), 246. 



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