THE SKELETON IN THE FLYING LEMURS. 193 



a deep notch marks the boundary between the two sigmoid cavities, wliile 

 on the opposite side the limiting border is continuous and distinctly 

 circular in outline (figure 9). It is imnecessar}' to add that such an 

 ulna as Oynocephalus possesses takes no part in the carpal articulation. 



The bones of the arm and forearm vary among the Insectivora to a 

 very marked, degree ; as, for example, among the hedgehogs, moles, and 

 shrews; and it is said that the ulna in Macroscelides and Petrodromm 

 is atrophied distally as in the colugo, but whether in these animals it 

 coossifies with the radius at that end may be open to question. 



According to Flower: 



Among the insectivora, tlie scaphoid and lunar (in the carpus) coalesce in 

 Galeopitheciis, Tupdia, Gentetes, Solenodon, Erinaceus, and Gyninura, but in 

 most of the other forms tliese bones are distinct. A distinct os centrals is found 

 in all except Galeopitheciis, Potamogale, Chrysoohloris, and Sorexr* 



A very careful microscopical examination of two wrists, or carpi, in 

 two diif erent specimens of the material at hand, proves beyond all question 

 that this statement, in so far as (Jynocephahis is concerned, is quite in- 

 correct. All of the eight usual bones of the carpus are to be found in 

 this animal. They are especially well developed in the manus of Steere's 

 specimen, the one from the right pectoral limb having been very carefully 

 examined by me under a high-power lens. There are four bones in the 

 proximal, and an equal number in the distal row. 



Commencing at the inner end of the proximal row (ulnar side) we 

 find the pisiform to be represented by a rather large, elongate ossicle 

 that has a facet upon its mesial aspect merging with another distally, the 

 first articulating with the cuneiform, and the latter with the unciform, 

 as in the Felidfe and probably other mammals. Cuneiform, one-third 

 larger than pisiform, is of an irregular cuboidal shape, with a small facet 

 for pisiform, and a larger one for unciform and semilunar, the latter 

 being much concaved. 



The semilunar is larger than any three of the other carpal bones taken 

 together, and is the only one of the wrist that articulates with the former. 

 This it dees with its large semi-ellipsoidal facet on its proximal aspect, 

 intended for the articulation at the distal end of the radius. Its outer 

 extremity also has a rather large, nearly circiilar, facet with which the 

 scaphoid articulates. Distally, the bone presents a raised, ridgelike, longi- 

 tudinal articulation for the trapezium; this is separated by a deep 

 groove from a larger, central, likewise loiigitudinal, raised facet which 

 articulates with trapezoid and os magnum. More internally it offers a 

 small articular surface to the unciform. Thus it will be seen that the 

 semilunar articulates with no fewer than seven bones, viz : radius, 

 cimeiform. 



=* Osteology of the Mammalia (1885), 289. This authority's description of 

 the hand in the inseetivores will hardly apply with accuracy to the colugo which 

 is unusually large. 



