BY DR. R. W. SHUFELDT, CM Z S. 107 



Owen further states that "the sacrum consists of two 

 "vertebrae in Ornithorhy7ichus and three in the Echidna. 

 "There are thirteen caudal vertebra in the Echidna, Fig. 

 "201. The first is the largest, with broad transverse pro- 

 "cesses, the rest progressively diminishing, and reduced, in 

 "the six last, to the central element. The Ornitlio7'hynchus, 

 "Fig. 199, has twenty-one caudal vertebrae, of which all but 

 "the last two have transverse processes, and the first eleven 

 "have also spinous and articular processes" (p. 317). The 

 cuts cited are the old figures that illustrated Owen's article 

 on the Monotremes in the third volume of the Cyclopedia of 

 Anatomy (1841) ; they are very crude, especially the one of 

 the Echidna, wherein the number of vertebrae do not agree 

 with the number for the Echidna given in the text, and the 

 cervico-dorsal regions of the spine are altogether too 

 straight. 



Flower, in his above cited table, points out that one 

 species of Echidna has eleven caudal vertebrae, and another 

 ten; while in the text in the same work (p. 77) he says: — 

 "The Echidna has 12 caudal vertebrae." Again, in the table, 

 he states that the Ornithorhynchus has 20 caudals, while in 

 the text — same page — he informs us that this monotreme 

 "has 20 or 21 caudal vertebrae." 



On page 68 he again says that "the Ornithorhynchus has 

 "2 ankylosed sacral vertebrae, and the Echidna 3 or 4." In 

 the table he gives the Ornithorhynchus 3 sacral vertebrae. 

 These discrepancies occur throughout the literature of the 

 subject. 



Turning to the vertebrae and ribs of these three Army 

 Medical Museum specimens (Figs. 1, 2, 10, and 11), we find, 

 in the specimen No. 1304, 17 pairs of ribs, the six anterior 

 ones of which articulate with the sternum through sternal 

 or costal ribs. The leading pair of these costal ribs articulate 

 with the extreme outer angles of the presternum; while 

 the last pair, which are very thick for their anterior moieties 

 and more or less flattened posteriorly, articulate with the 

 ultimate joint of the true sternum. Following these, we 

 have 8 ribs that articulate below with costal ribs, the latter 

 being free, very broad, and compressed from above, down- 

 wards. Finally, in the last three pairs of these thoracic ribs 

 are "floating ribs," the last pair being but half the length 

 of the first pair, while the midpair is intermediate in length 

 between these and the first pair. This specimen has seven 

 cervical vertebrae; seventeen dorsals; two lumbars; four 

 sacrals; and twenty caudals (counting the terminal one 

 which has been lost). 



