1894 NOTES AND COMMENTS. 247 



in the mid-dorsal line being reduced and obliterated by the union of 

 the longitudinal portions of the folds to form the neural canal. 

 Attention was also drawn to the facts that the medullary folds of 

 Tornaria not only arise in close relation with the degenerating posterior 

 portion of the ciliated band, but take a course which is identical with 

 it ; and that the region of the neural tube is just that area where the 

 convoluted ciliated bands approximate most closely in the dorsal region 

 of the body. 



The position of the gill-slits in Balanoglosstis behind, and in 

 Chordata in front of, the neural loop was attributed to that peculiar 

 change of position which the primitively caecal gill-pouches of 

 Balanoglosstis undergo during the period of metamorphosis, as observed 

 and described both by Agassiz and Morgan. 



Pending the appearance of the author's complete account, we need 

 say no more here, except, perhaps, that Mr. Garstang finds in the 

 peculiar adoral ciliated band of Auricularia the exact precursor of the 

 combined peripharyngeal bands and the marginal bands of the endo- 

 style of the Tunicata and ^ mphioxiis. 



The Ancestry of Modern Mammalia. 



In the American Journal of Science, Professor O. C. Marsh is 

 continuing his valuable brief notes on the remains of Tertiary 

 mammals from the western regions of North America, while Pro- 

 fessors Cope, Scott, and Osborn, and Mr. Earle, are engaged upon 

 more elaborate memoirs. Progress is thus rapid in the northern half 

 of the New World, and Mr. Lydekker has spent the autumn in further 

 work upon the remarkable extinct Tertiary mammalia, chiefly sloths 

 and armadillos, in its southern half. Of greatest interest, however, is 

 the announcement that the general public in North America will soon 

 have the opportunity of seeing these extinct quadrupeds displayed in 

 an easily comprehensible manner, so that they can judge of the beasts 

 for themselves. Except at Princeton, the collections of mammalian 

 remains have hitherto been stowed away almost like goods in a store ; 

 but the American Museum of Natural History has now for some 

 time secured the services of several good collectors, including Mr. J. 

 B. Hatcher, and numerous entire skeletons of the most typical 

 Tertiary animals are, as a result, at present being mounted for the 

 exhibition rooms. Professor Osborn, of Columbia College, is super- 

 intending the work, and as the mounting proceeds, drawings of the 

 actual specimens will be published. 



European Pleistocene Mammalia. 



In Europe similar studies are also progressing favourably, and an 

 enterprising dealer, we understand, has been making extensive excava- 



