REPTILIA : LIMNOSCELIS 



37 



two bones in each specimen lie with the thin ends nearly in apposi- 

 tion, as though they had joined each other in life. 



Humerus. — The humerus is a remarkably short and thickset 

 bone, resembling that of Diadectes more closely than that of any 

 other genus that I know. The ectocondyle is more expanded and 

 turned inward than in that genus, however, nor is the proximal 

 expansion so much twisted from the plane of the entocondyle as 

 is the case with the humeri 

 of more terrestrial Permian 

 reptiles. The entepicondylar 

 foramen is large, situated not 

 far from the lower extremity 

 of the lateral process. The 

 ulnar expansion is broad and 

 flat, and occupies a plane di- 

 vergent from that of the proxi- 

 mal inner side of about forty- 

 five degrees. The capitellum 

 is very large and rounded, 

 situated on the outer angle 

 of the bone, as seen from the 

 ventral side, and is remark- 

 ably close to the lateral pro- 

 cess. The ectocondyle is 

 remarkably stout and protu- 

 berant, and is directed almost 

 rectangularly, or even at an 

 acute angle backward, termi- 

 nating very near the middle of the bone transversely, and above the 

 groove for the ulna on the dorsal side. It is an interesting fact 

 that not only the structure of the humerus, but also the whole 

 anterior limb, resembles not only that of Diadectes, but also that 

 of the amphibian Eryops, suggesting similar habits in all three ani- 

 mals, and possibly, too, genetic affinities. There is a moderately 

 stout ectepicondylar process, as in Desmospondylus, Seymour ia, 

 Diadectes, Eryops, etc. It is situated a little below the lateral pro- 

 cess on the radial side. 



Fig. 12. — Limnoscelis paJitdis. Left 

 capula, with clavicle and cleithrum, two- 

 hfths natural size, sc, scapula; c, cleithrum; 

 <7, clavicle. 



