Huene and Lull — Triassic Reptile Hallopus. 113 



Art. XIII. — On the Triassic Reptile, Hallopus Victor Marsh ; 

 by F. R. von Huene, Tubingen, Germany, and R. S. Lull, 

 New Haven, Conn. 



A reexamination of the type specimen of Hallopus, pre- 

 served in the Peabocly Museum at Yale, has brought forth 

 some interesting new facts. We are giving here a short pre- 

 liminary description and intend later to write a fully illustrated, 

 detailed treatise in which Hallopus will be compared with 

 other reptiles and its true relationships investigated. 



Following Williston,* the Hallopus beds at Garden Park, 

 near Laramie City, Wyoming, supposed by Marsh to be Juras- 

 sic, are Upper Triassic. The type specimen is contained in 

 two slabs of red sandstone fitting together and, while fairly 

 well preserved, in some instances only the impression of .the 

 bone upon the matrix remains, adding to the difficulty of an 

 exact interpretation. 



Vertebral. — There is one doubtful cervical vertebra, a doubt- 

 ful broad and low neural spine of a dorsal vertebra, two sacral s 

 and foul' anterior caudals, the latter still in connection with 

 each other. 



The sacrals show their upper surface in the smaller slab, 

 but the greater part of the upper arches is missing. They 

 are coossified, slightly elongated and possess strong sacral 

 ribs, the second one being much stronger than the first. 

 The direction of the first sacral rib is a little forward and that 

 of the second more backward, the latter being longer than the 

 former. The ventral part of the second sacral rib expands 

 towards the first sacral rib so that they come in connection. 



mm 



Length of both sacral vertebras together 20 



Their width where they are coossified 6 



Length of the right first sacral rib from the me- 

 dian line of the neural canal 11 -5 



Length of the left second sacral rib from the 

 median line of the neural canal 16 



Width of the first sacral rib at its narrowest 



place in the middle.. 4-5 



Width of the second sacral rib at its narrowest 



place in the middle . 7'5 



From the anterior edge of distal extremity of 

 the first to the posterior edge of distal extrem- 

 ity of the second sacral rib 30 



The caudal centra are not constricted in the middle and only 

 little longer than high. The neural spines are broad and bent 

 backward. ; the zygapophyses are fairly large. 



* Williston, 1905. 



