OF BAL^EXOPTERA MUSCULUS 



225 



Fig. 11. 



Pelvic Bones. 

 Fig. 11, in text, and PLate vi, fig. 14 (inverted). 



One pelvic bone (the left) was removed without being noticed from the body during dis- 

 section. When we perceived that the proper place had been passed a long search was 

 made among the pieces of Hesh which had been cut off, and the bone at last found. I was 

 so fortunate as to find the bone 

 of the right side in its original 

 position. The rudimentary fe- 

 mur was found on each side. 

 The pelvic bone is thin and 

 triangular. The outer surface 

 is slightly concave ; the inner 

 slightly convex. The processes 

 are thicker than the body, par- 

 ticularly the anterior, which is 

 the longest and is flattened 

 below. The inferior border is 

 slightly concave, pretty sharp 

 in the middle, but thick and 

 flat towards the ends. The superior process is broader than the others, but is not much 

 thicker than the body of the bone. The anterior superior border is interrupted by a small 

 notch in the bone of the right side ; but that of the left does not show any trace of an in- 

 dentation. 



The greatest length of the bone of the left side is 8 1-2 inches ; of that of the right side 

 9 inches. The greatest vertical depth is 3 inches on the left and 3 1-2 inches on the right 

 side. 



The rudimentary femora were chiefly cartilaginous ; but each contained a semi-ossi- 

 fied nucleus. An error in the dissection made their position a matter of some doubt. 

 They were probably situated in front of the position in which they are drawn. 



Organ of Hearin'G. 



The auditory apparatus was not studied in the fresh state ; the description therefore 

 refers only to the bones. This specimen differs from those of the B. rostrata by the 

 firmness with which the petrous and tympanic bones were fixed in the skull. Drs. 

 Carte and Macalister state that the connection was slight, and that the part in ques- 

 tion was removed without much difficulty. In this case, on the other hand, the posterior 

 portion was so much overlapped by the squamous and exoccipital bones, that a large 

 piece of the former had to be removed to free it, as well as a scaly plate belonging to 

 the pterygoid, which covered the anterior portion. The right ear was the only one ex- 

 amined. It presents the usual solidity, weighing three pounds, and is divided into the 

 tympanic bulla and into the anterior, posterior and labyrinthic portions of the petrous 

 bone proper. 



The Tympanic Bulla presents no peculiarities which appear specific ; it resembles the 

 drawing of that bone from the B. rostrata quite as much as those from the B. muscnhis. 



MEMOIRS. BO>T. SOC. NAT. H!eT. VOL. II. 57 



