APPENDIX. 
Art. XLL—A New Order of Extinct Jurassic Reptiles ( Caeluria); 
by O. C. Marsu. With Plate X. 
THE remains previously described by the writer, and named 
Colurus fragilis,* prove on further investigation to represent a 
new group of much interest. Portions of the skeleton of 
Some ten or twelve different individuals have now been se- 
cured from the same horizon in the upper Jurassic that yielded 
the type specimen, and all are in the Museum of Yale College. 
. 
with certainty. 
€ most marked feature in all the known remains of 
Celurus is the extreme lightness of the bones, the excavations 
: : 4 
are proportionally larger than in either Pterodactyls or Birds, 
meutl ok < : P 
caudal vertebra are figured, with transverse sections of each to 
lustrate this point. Even the ribs of Ctelurus are hollow, 
with well defined walls to their large cavities. No limb bones 
of Celurus are as yet known with certainty, and those pro- 
visionally referred to that genus are, owing to their fragility, 
Panentetly preserved for accurate determination. 
* This Journal, vol. xviii, p. 504, Dec., 1879. 
