A MONOGRAPH OF THE BATS OF NORTH AMERICA. 19 



complete and is coini)Ose(l of a proximal and a distal rudiment. The 

 proximal rudiment is free at the weak olecranon, which resembles the 

 parts in the sloth, and is continn )us in nn)st jienera with an arched 

 rod-like shaft of uniform width, which is ossihed, as a rule, with thera- 

 dius at about its proximal third. Exceptions are noted to this arrange- 

 ment in some of the vespertilionine jjenera, c. f/., Scotophilns and Mini- 

 opteruH^ as well as in the molossine Promops, in which a small anchy- 

 losed olecranon unites by a filiform shaft to the i)roximal third of the 

 ulna. But the vespertilionine forms as a rule (Rarpioce^yhalus not ex- 

 amined) retain a free olecranon which is continuous with a filiform ta- 

 pering shaft, which ends free in the muscles of the forearm. Coryno- 

 rhinus, Xijctophilus, Chalinolobus are exceptions even to this arrange- 

 ment, for here the shaft is entirely absent, the rudimental fixed olecra- 

 non constituting the entire proximal end. The tendon of the triceps 

 muscle as it is inserted into the ulna is occupied by a sesamoid bone. 

 No other animals possess a bone in this situation. It is either a sepa- 

 rate ossicle dev^eloped in the tendon, or the disjuncted epiphysis of the 

 ulna. This relatively unimportant bone receives the muscle which 

 alone extends the powerful forearm. The extensor carpi ulnar is a 

 muscle as constant in this group as in others — arises from it. All the 

 relations of the ulna, therefore, are with the extensors. The distal end 

 is anchylosed to the radius at the wrist. The form may be that of a 

 quadrate plate, more or less well defined, which is usually entire, though 

 it may retain a minute foramen of insufticiency, as a rule, in the ves- 

 pertilioniues and molossines. The plate may be absent when a hook- 

 like proeess directed proximally, as in Atalapha; it may project nearly at 

 right angles to shaft and be conoidal, as in phyllostomines, rhinolo- 

 phines, and the genera Saccopteryx and Natalus; or it may be absent, 

 as in the pteropines. 



The carpus of bats exhibits some valuable characters. In all forms 

 the first row of bones is composed of two bones only — viz, a large bone 

 which (constitutes the greater part of the row and will here receive the 

 name of the scapho-Iuuar, and a small separate bone at the ulna border 

 of the scapho-lunar which appears fro be the cuneiform. 



The second row is composed of the traj^ezium, trai)ezoid, os magnum, 

 unciform, and often the pisiform. The os magnum and unciform always 

 unite to form a convex surface for articulation with the second row. With 

 the exception of the pisiform all these integers are easily recognized. 

 The carpus on the whole is simple, since the first, second, and third 

 metacarpal bones are in axial articulation with trapezium, trapezoid, 

 and OS magnum, respectively, while the fourtli and fifth metacarpal 

 bones articulate with the unciform. 



In pteropines the trajjezium and os magnum are greatly larger than 

 are the other bones of the second row, and give a peculiarly nuissive 

 appearance to the carpus when the wing is folded. The bone first 

 named is without nodosity on the palmar aspect. "Wedged between 



