182 DR. R. W. SHUFELDT ON - [Apr. 1, 



defined digitations from the outer surfaces of the majority of the 

 remaining abdominal ribs in a line along the external border of the 

 sacro-luynbalis of the same side. For its entire length, mesiad, the 

 muscle now under consideration apparently blends with the rectus 

 abdominis, and I fail to find any other insertion for it. It is quite 

 possible that the part I describe above as being attached to the 

 integuments overlying the thorax, may more properly be considered 

 as belonging to the rectus, as the nl)res therefrom seem to extend 

 down the body ; the two muscles are quite closely blended here. 



76. Obliqnus abdominis internus. — In HeJoderma suspectum the 

 thirty-first to the thirty-third vertebrae, inclusive, bear very short 

 ribs, and consequently upon the ventral aspect of its body there is a 

 region which is devoid of special bony protection. It is here that 

 the present muscle spreads out and by its muscular wall largely 

 protects what would otherwise be a weak point. It arises by a 

 strong tendon from the anterior border of the ilium of the same 

 side, and, passing forwards and inwards, it gradually merges 

 anteriorly with the lower part of the intercostals and the abdominal 

 fascia of the region in question. 



77. Transversalis. — The transverse fibres of this muscle are at 

 once made apparent upon dissecting away the last-described muscle, 

 and it is found also to be ])riacipally confined to the lower prepelvic 

 region of the abdomen. It comes away as fascia from the external 

 border of the quadratus lumborum, while, mesially, its strong fascia 

 blends with the fascia of the transversalis of the opposite side, and 

 is carried up beneath the rectus to a point nearly as high as thecosto- 

 sternal ribs. 



78. Quadratus lumborum. — This muscle is beautifully developed 

 in the reptile before us. It arises by means of a dense, sheet-like 

 fascia from tlie anterior rim of the ilium of the same side, and from 

 the adjacent border of the diapophysis of the first sacral vertebra as 

 far in as its centrum. Soon becoming muscular, its fibres passing 

 directly forwards insert themselves into the entire length of the 

 posterior surface of the rib to the thirtieth vertebra. Yentrally, it 

 also attaches itself to the dorsal surfaces of the so nominated " lumbar 

 ribs," en passant, by tendinous anchorages. 



79. External intercostals.— The internal and external intercostals 

 are both separately and very strongly developed in our present sub- 

 ject. Together they fill in all the spaces among the vertebral ribs, 

 as well as between the sterno-costal hfemapophyses. 



Taken in mid-region, an external intercostal arises from the entire 

 anterior surface of the rib, save from about half a centimetre of its 

 vertebral extremity, and its fibres passing forwards and upwards thev 

 are inserted into the entire posterior surface of the next anterior rib, 

 save for a short distance above its free extremity. Between the 

 sternal ribs the fibres of the external intercostals pass directly for- 

 wards, and, in each case, very nearly fill in the entire space. We 

 observe that from the sternum backwards through the pleura- 

 po])hysial series there are muscular fibres coming away from the free 

 ends of the ribs, for about half a centimetre of their lengths in 



